Through systematic literature review,this study constructs a relationship model of the impact of inbound open innovation on firm innovation performance,and introduced two-dimensional business model design(novelty and ...Through systematic literature review,this study constructs a relationship model of the impact of inbound open innovation on firm innovation performance,and introduced two-dimensional business model design(novelty and efficiency)as mediation variables.It is preliminary confirmed theoretically that inbound open innovation has a positive impact on firm innovation performance,and the rationality of business model playing a mediation role in the relationship between inbound open innovation and innovation performance.Through questionnaire survey and empirical analysis,it is concluded that inbound open innovation has a positive impact on firm innovation performance;Two-dimensional business model design(novelty and efficiency)play a completely positive mediation role in the relationship between inbound open innovation and innovation performance.Based on these findings,this paper developed recommendations for future research.展开更多
In this project,the miniaturization of the aircraft was realized under the premise of strong maneuverability,high concealability,and driving a certain load,and the flight mode and structural characteristics of birds w...In this project,the miniaturization of the aircraft was realized under the premise of strong maneuverability,high concealability,and driving a certain load,and the flight mode and structural characteristics of birds were imitated.A small bionic flapping wing aircraft was built.The flapping of the wing was realized by the crank slider mechanism,and the sizes of each part were calculated according to the bionics formula.The wingspan was 360.37 mm,the body width was 22 mm,the body length was 300 mm,the wing area was 0.05 m^(2),the flapping amplitude was 71°.ADAMS software was used to simulate the dynamics of the designed aircraft,and the variation of flapping amplitude and angular velocity during the movement of the aircraft was obtained,which verified the feasibility of the mechanism.The prototype aircraft was made for flight test,and the designed bionic flapping wing aircraft achieved the expected effect.It provides a theoretical basis and data support for the design and manufacture of small flapping wing aircraft.展开更多
A simplified calculation of the specimen’s stress-strain curve is generally conducted using the two-wave method by the split Hopkinson pressure bar(SHPB),which aligns the onset of the transmitted and reflected waves....A simplified calculation of the specimen’s stress-strain curve is generally conducted using the two-wave method by the split Hopkinson pressure bar(SHPB),which aligns the onset of the transmitted and reflected waves.However,this approach neglects the travel time of elastic waves within the specimen.Considering the travel time of elastic waves,this study quantitatively investigates the error characteristics and patterns of stress,strain,and strain rate in the specimen under different conditions using the theoretical two-wave method,and compares the results with those obtained using the onset-aligned twowave method.The study reveals that the stress-time curves derived from the theoretical two-wave method are lower than the actual stress curves,whereas those obtained from the onset-aligned two-wave method are consistently higher than the actual stress curves,with the stress deviation approximating a constant value when the dimensionless time exceeds 2.0.The starting point of the stress-strain curves obtained by the theoretical two-wave method is not zero but a point on the strain axis,whereas the onset-aligned two-wave method always starts at zero.However,the slopes of the stress-strain curves obtained by both methods differ from the actual Young’s modulus of the material,and functional relationships between the slopes and the actual Young’s modulus are provided.This research offers theoretical guidance for the refined design of SHPB experiments and the accurate processing of data.展开更多
Brucellosis is a zoonosis that causes economic losses worldwide,as well as human morbidity and poverty.It is caused by Brucella spp.,which are animal pathogens~([1]).Among the 13 identified species,Brucella melitensis...Brucellosis is a zoonosis that causes economic losses worldwide,as well as human morbidity and poverty.It is caused by Brucella spp.,which are animal pathogens~([1]).Among the 13 identified species,Brucella melitensis is the most common and is frequently isolated from both humans and livestock~([2]).展开更多
The editor regrets that they inadvertently pasted the wrong figure during the production stage.The correct Fig.7 should be as below:The editor would like to apologise for any inconvenience caused.
This study presents a theoretical analysis of the perforation process of finite-thickness metal plates(with a thickness ratio of T_0/D = 0.6–1.5) under normal impact by spherical-nosed projectiles. The model is valid...This study presents a theoretical analysis of the perforation process of finite-thickness metal plates(with a thickness ratio of T_0/D = 0.6–1.5) under normal impact by spherical-nosed projectiles. The model is validated over an impact velocity range of 180–1247 m/s. The entire penetration process is divided into three stages: the crater formation stage, the steady stage, and the shear stage. A thicknessdependent dynamic cavity expansion resistance model is first introduced to quantitatively describe the axial resistance experienced by the projectile during the tip-entry and steady stages. Subsequently, a thickness-related damage parameter is proposed to refine the resistance expression during the transition from the steady stage to the shear stage, thereby eliminating discontinuities in resistance across stages. When the projectile fully perforates the target, the model predicts a gradual decay of resistance to zero as the residual ligament thickness vanishes, which better reflects the actual physical behavior. The model is validated using four sets of experimental conditions. In addition, to illustrate the model's applicability more intuitively, a numerical simulation case from the literature is reproduced, and the resulting resistance-time curve is compared with the model output. The results demonstrate that the proposed model agrees well with experimental data in terms of residual velocity, ballistic limit, and penetration resistance. Finally, a method for adjusting the threshold parameter within the resistance function is provided, and the influence of this coefficient on the model predictions is discussed.展开更多
This paper explores the applicability of the generalized wave impedance hypothesis in split Hopkinson pressure bar(SHPB)experiments,particularly under non-ideal conditions.The study investigates the effects of changes...This paper explores the applicability of the generalized wave impedance hypothesis in split Hopkinson pressure bar(SHPB)experiments,particularly under non-ideal conditions.The study investigates the effects of changes in wave impedance ratio and cross-sectional area ratio on the dynamic response of materials at high strain rates.Through theoretical analysis and numerical simulation,the impact of different wave impedance and cross-sectional area ratios on stress wave propagation characteristics is discussed in detail.It is found that when the cross-sections of two bars differ,shear strain occurs at the abrupt cross-section,leading to waveform distortion in the transmitted and reflected waves.The force balance condition does not always align with the momentum conservation theorem,and only when the three waveforms and wavelengths are completely consistent do they align.The research shows that when the wave impedance ratio and cross-sectional area ratio are within a specific range,the generalized wave impedance hypothesis can accurately predict changes in Young’s modulus and density.Additionally,the study extends the exploration to key factors such as wave impedance ratio,wave speed,Young’s modulus,density,and area ratio.展开更多
Shearing dislocation is a common failure type for rock–backfill interfaces because of backfill sedimentation and rock strata movement in backfill mining goaf.This paper designed a test method for rock–backfill shear...Shearing dislocation is a common failure type for rock–backfill interfaces because of backfill sedimentation and rock strata movement in backfill mining goaf.This paper designed a test method for rock–backfill shearing dislocation.Using digital image techno-logy and three-dimensional(3D)laser morphology scanning techniques,a set of 3D models with rough joint surfaces was established.Further,the mechanical behavior of rock–backfill shearing dislocation was investigated using a direct shear test.The effects of interface roughness on the shear–displacement curve and failure characteristics of rock–backfill specimens were considered.The 3D fractal dimen-sion,profile line joint roughness coefficient(JRC),profile line two-dimensional fractal dimension,and the surface curvature of the frac-tures were obtained.The correlation characterization of surface roughness was then analyzed,and the shear strength could be measured and calculated using JRC.The results showed the following:there were three failure threshold value points in rock–backfill shearing dis-location:30%–50%displacement before the peak,70%–90%displacement before the peak,and 100%displacement before the peak to post-peak,which could be a sign for rock–backfill shearing dislocation failure.The surface JRC could be used to judge the rock–backfill shearing dislocation failure,including post-peak sliding,uniform variations,and gradient change,corresponding to rock–backfill disloca-tion failure on the field site.The research reveals the damage mechanism for rock–backfill complexes based on the free joint surface,fills the gap of existing shearing theoretical systems for isomerism complexes,and provides a theoretical basis for the prevention and control of possible disasters in backfill mining.展开更多
This study examines the penetration of 12.7 mm armor piercing incendiary projectiles into SiC ceramic-fiber composite target plates.By observing the recovered projectile and the overall damage morphology of the cerami...This study examines the penetration of 12.7 mm armor piercing incendiary projectiles into SiC ceramic-fiber composite target plates.By observing the recovered projectile and the overall damage morphology of the ceramic-fiber composite target plates.Additionally,multi-level screening and weighing of the recovered projectile and ceramic fragments revealed that the mass distribution of the projectile and ceramic fragments under different backing structures conforms to a powerlaw distribution.Experimental results indicate that for single laminate as the backing,the fragmentation of the projectile and ceramics is highest when T300 is the material.Incorporating a T300 transition layer between the SiC ceramic and aramid fibers(Kevlar)or ultra-high molecular weight polyethylene(UHMWPE)increases the fragmentation of the projectile and ceramics,leading to increased energy absorption.The projectile’s head mainly exhibits pulverized abrasive fragmentation,while larger projectile fragments primarily result from shear and tensile stress-induced shear-tensile failure fractures.The primary damage mode of ceramics under high-speed impact is the expansion of ceramic cones and radial cracks.The main form of damage in UHMWPE laminate is interlayer separation caused by tensile waves,permanent plastic deformation at the back protrusion,and perforation failure primarily due to shear waves.The damage mode of Kevlar laminate is similar to that of UHMWPE,with the distinction being that Kevlar laminate primarily exhibits perforation failure caused by tensile waves.Carbon fiber T300 laminate damage mainly consists of cross-shaped brittle fractures caused by shear waves.展开更多
To enhance the protective performance of ceramic composite armor,ballistic penetration experiments were conducted on Al_(2)O_(3) ceramic-ultra-high molecular weight polyethylene(UHMWPE)composite armor with different t...To enhance the protective performance of ceramic composite armor,ballistic penetration experiments were conducted on Al_(2)O_(3) ceramic-ultra-high molecular weight polyethylene(UHMWPE)composite armor with different thickness configurations.The damage and failure modes of hard projectiles and ceramic-fiber composite targets were analyzed.The recovered projectiles and ceramic fragments were sieved and weighed at multiple stages,revealing a positive correlation between the degree of fragmentation of the projectiles and ceramics and the overall ballistic resistance of the composite targets.Numerical simulations were performed using the LS-DYNA finite element software,and the simulation results showed high consistency with the experimental results,confirming the validity of the material parameters.The results indicate that the projectile heads primarily exhibited crushing and abrasive fragmentation.Larger projectile fragments mainly resulted from tensile and shear stress-induced failure.The failure modes of the composite targets included the formation of ceramic cones and radial cracks under high-velocity impacts.The UHMWPE laminated plates exhibited interlayer separation caused by tensile waves,permanent plastic deformation of the rear surface bulging,and perforation failure primarily due to shear forces.Through extended numerical simulations,while maintaining the same areal density and configuration of9 mm Al_(2)O_(3) ceramic+12 mm UHMWPE laminated composite armor,the thickness configurations of the Al_(2)O_(3) ceramic and UHMWPE laminated backplates were varied,and various thicknesses of UHMWPE laminates were simulated as the cover layer for the ceramic panels.The simulation results indicated that the composite armor configuration of 10 mm Al_(2)O_(3) ceramic+8 mm UHMWPE composite armor increased energy absorption by13.48%.When altering the cover layer thickness,a 4 mm UHMWPE+9 mm Al_(2)O_(3)+8 mm UHMWPE composite armor demonstrated a 27.11%improvement in energy absorption,showing a relatively significant enhancement.展开更多
In the era when online shopping economy and online economy increasingly dominate social consumption,WeChat shopping has increasingly become a way that everyone accepts and is willing to try.This study applied Technolo...In the era when online shopping economy and online economy increasingly dominate social consumption,WeChat shopping has increasingly become a way that everyone accepts and is willing to try.This study applied Technology Acceptance Model commonly used in the field of information technology and rational behavior theory to the field of consumer behavior,and used the perceived ease of use and perceived usefulness in the technology acceptance model to explain consumers'willingness to use WeChat shopping.At the same time,the moderating effect of consumer innovativeness was also studied.The empirical results show that the main effect of perceived ease of use and usefulness is significant,and the moderating effect of consumer innovativeness is not significant.Based on the research results,the study puts forward the corresponding countermeasures and suggestions.展开更多
Lipid metabolism disorders contribute to hyperlipidemia and hepatic steatosis.It is ideal to develop drugs simultaneous improving both hyperlipidemia and hepatic steatosis.Nitazoxanide is an FDA-approved oral antiprot...Lipid metabolism disorders contribute to hyperlipidemia and hepatic steatosis.It is ideal to develop drugs simultaneous improving both hyperlipidemia and hepatic steatosis.Nitazoxanide is an FDA-approved oral antiprotozoal drug with excellent pharmacokinetic and safety profile.We found that nitazoxanide and its metabolite tizoxanide induced mild mitochondrial uncoupling and subsequently activated AMPK in Hep G2 cells.Gavage administration of nitazoxanide inhibited high-fat diet(HFD)-induced increases of liver weight,blood and liver lipids,and ameliorated HFD-induced renal lipid accumulation in hamsters.Nitazoxanide significantly improved HFD-induced histopathologic changes of hamster livers.In the hamsters with pre-existing hyperlipidemia and hepatic steatosis,nitazoxanide also showed therapeutic effect.Gavage administration of nitazoxanide improved HFD-induced hepatic steatosis in C57BL/6J mice and western diet(WD)-induced hepatic steatosis in Apoe-/-mice.The present study suggests that repurposing nitazoxanide as a drug for hyperlipidemia and hepatic steatosis treatment is promising.展开更多
Our previous studies found that mitochondrial uncouplers CCCP and niclosamide inhibited artery constriction and the mechanism involved AMPK activation in vascular smooth muscle cells. BAM15 is a novel type of mitochon...Our previous studies found that mitochondrial uncouplers CCCP and niclosamide inhibited artery constriction and the mechanism involved AMPK activation in vascular smooth muscle cells. BAM15 is a novel type of mitochondrial uncoupler. The aim of the present study is to identify the vasoactivity of BAM15 and characterize the BAM15-induced AMPK activation in vascular smooth muscle cells(A10 cells). BAM15 relaxed phenylephrine(PE)-induced constricted rat mesenteric arteries with intact and denuded endothelium. Pretreatment with BAM15 inhibited PEinduced constriction of rat mesenteric arteries with intact and denuded endothelium. BAM15, CCCP,and niclosamide had the comparable IC50 value of vasorelaxation in PE-induced constriction of rat mesenteric arteries. BAM15 was less cytotoxic in A10 cells compared with CCCP and niclosamide.BAM15 depolarized mitochondrial membrane potential, induced mitochondrial fission, increased mitochondrial ROS production, and increased mitochondrial oxygen consumption rate in A10 cells.BAM15 potently activated AMPK in A10 cells and the efficacy of BAM15 was stronger than that of CCCP, niclosamide, and AMPK positive activators metformin and AICAR. In conclusion, BAM15 activates AMPK in vascular smooth muscle cells with higher potency than that of CCCP, niclosamide and the known AMPK activators metformin and AICAR. The present work indicates that BAM15 is a potent AMPK activator.展开更多
In this paper,we study three types of Cantor sets.For any integer m≥4,we show that every real number in[0,k]is the sum of at most k m-th powers of elements in the Cantor ternary set C for some positive integer k,and ...In this paper,we study three types of Cantor sets.For any integer m≥4,we show that every real number in[0,k]is the sum of at most k m-th powers of elements in the Cantor ternary set C for some positive integer k,and the smallest such k is 2~m.Moreover,we generalize this result to the middle-1/αCantor set for1<α<2+√5 and m sufficiently large.For the naturally embedded image W of the Cantor dust C×C into the complex plane C,we prove that for any integer m≥3,every element in the closed unit disk in C can be written as the sum of at most 2^(m+8)m-th powers of elements in W.At last,some similar results on p-adic Cantor sets are also obtained.展开更多
As deep borehole heat exchangers(DBHEs)extract heat from geothermal energy with depth of 2–3 kilometers,the circulation water pressure drop is larger than that of shallow-depth borehole heat exchangers,influenced by ...As deep borehole heat exchangers(DBHEs)extract heat from geothermal energy with depth of 2–3 kilometers,the circulation water pressure drop is larger than that of shallow-depth borehole heat exchangers,influenced by the water flow rates.This paper conducted field tests and simulation analysis to study the heat transfer performance and water circulation resistance of DBHE in coupled,where the natural circulation characteristic has been discovered and analyzed quantitatively.Results show that the water temperature and density variation along DBHE forms the driving force of natural circulation.For mechanical flow rate of 6.0 kg/s and inlet water temperature of 20.0℃,the natural circulation flow rate reaches about 2.2 kg/s with transient heat extraction power of 78.5 kW,without energy consumption of water pumps.And the larger inlet water temperature,smaller mechanical water flow rate,higher inner tube thermal conductivity coefficient and larger depth of DBHE all contribute to the larger natural circulation water flow rate.In addition,the natural circulation could effectively decrease the comprehensive water pressure drops of DBHE,which is about 47.3%smaller than the calculated value of traditional models.Thus the natural circulation characteristic has significant influence on the heat transfer performance of DBHE,and also on the energy performance of whole heat pump systems.展开更多
基金supported by MOE(Ministry of Education in China)Project of Humanities and Social Sciences(No.20YJC630022)Shandong Province Natural Science Foundation(No.ZR2017MG033)Fundamental Research Funds for the Central Universities(No.HIT.HSS.201875).
文摘Through systematic literature review,this study constructs a relationship model of the impact of inbound open innovation on firm innovation performance,and introduced two-dimensional business model design(novelty and efficiency)as mediation variables.It is preliminary confirmed theoretically that inbound open innovation has a positive impact on firm innovation performance,and the rationality of business model playing a mediation role in the relationship between inbound open innovation and innovation performance.Through questionnaire survey and empirical analysis,it is concluded that inbound open innovation has a positive impact on firm innovation performance;Two-dimensional business model design(novelty and efficiency)play a completely positive mediation role in the relationship between inbound open innovation and innovation performance.Based on these findings,this paper developed recommendations for future research.
文摘In this project,the miniaturization of the aircraft was realized under the premise of strong maneuverability,high concealability,and driving a certain load,and the flight mode and structural characteristics of birds were imitated.A small bionic flapping wing aircraft was built.The flapping of the wing was realized by the crank slider mechanism,and the sizes of each part were calculated according to the bionics formula.The wingspan was 360.37 mm,the body width was 22 mm,the body length was 300 mm,the wing area was 0.05 m^(2),the flapping amplitude was 71°.ADAMS software was used to simulate the dynamics of the designed aircraft,and the variation of flapping amplitude and angular velocity during the movement of the aircraft was obtained,which verified the feasibility of the mechanism.The prototype aircraft was made for flight test,and the designed bionic flapping wing aircraft achieved the expected effect.It provides a theoretical basis and data support for the design and manufacture of small flapping wing aircraft.
基金supported by the National Natural Science Foundation of China (Grant Nos.U2341244,12172179,and 11772160)the Postgraduate Research&Practice Innovation Program of Jiangsu Province.
文摘A simplified calculation of the specimen’s stress-strain curve is generally conducted using the two-wave method by the split Hopkinson pressure bar(SHPB),which aligns the onset of the transmitted and reflected waves.However,this approach neglects the travel time of elastic waves within the specimen.Considering the travel time of elastic waves,this study quantitatively investigates the error characteristics and patterns of stress,strain,and strain rate in the specimen under different conditions using the theoretical two-wave method,and compares the results with those obtained using the onset-aligned twowave method.The study reveals that the stress-time curves derived from the theoretical two-wave method are lower than the actual stress curves,whereas those obtained from the onset-aligned two-wave method are consistently higher than the actual stress curves,with the stress deviation approximating a constant value when the dimensionless time exceeds 2.0.The starting point of the stress-strain curves obtained by the theoretical two-wave method is not zero but a point on the strain axis,whereas the onset-aligned two-wave method always starts at zero.However,the slopes of the stress-strain curves obtained by both methods differ from the actual Young’s modulus of the material,and functional relationships between the slopes and the actual Young’s modulus are provided.This research offers theoretical guidance for the refined design of SHPB experiments and the accurate processing of data.
基金supported by a Gansu Province Health Industry Scientific Research Plan Project(No.GSWSKY2018-10)The Major Science and Technology Innovation Project of Gansu Provincial Health and Health Industry(GSWSKY2024-7)。
文摘Brucellosis is a zoonosis that causes economic losses worldwide,as well as human morbidity and poverty.It is caused by Brucella spp.,which are animal pathogens~([1]).Among the 13 identified species,Brucella melitensis is the most common and is frequently isolated from both humans and livestock~([2]).
文摘The editor regrets that they inadvertently pasted the wrong figure during the production stage.The correct Fig.7 should be as below:The editor would like to apologise for any inconvenience caused.
基金supported by the National Natural Science Foundation of China (Grant Nos.U2341244,12172179,11772160)。
文摘This study presents a theoretical analysis of the perforation process of finite-thickness metal plates(with a thickness ratio of T_0/D = 0.6–1.5) under normal impact by spherical-nosed projectiles. The model is validated over an impact velocity range of 180–1247 m/s. The entire penetration process is divided into three stages: the crater formation stage, the steady stage, and the shear stage. A thicknessdependent dynamic cavity expansion resistance model is first introduced to quantitatively describe the axial resistance experienced by the projectile during the tip-entry and steady stages. Subsequently, a thickness-related damage parameter is proposed to refine the resistance expression during the transition from the steady stage to the shear stage, thereby eliminating discontinuities in resistance across stages. When the projectile fully perforates the target, the model predicts a gradual decay of resistance to zero as the residual ligament thickness vanishes, which better reflects the actual physical behavior. The model is validated using four sets of experimental conditions. In addition, to illustrate the model's applicability more intuitively, a numerical simulation case from the literature is reproduced, and the resulting resistance-time curve is compared with the model output. The results demonstrate that the proposed model agrees well with experimental data in terms of residual velocity, ballistic limit, and penetration resistance. Finally, a method for adjusting the threshold parameter within the resistance function is provided, and the influence of this coefficient on the model predictions is discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2341244,12172179,11772160,and 12202207)China Postdoctoral Science Foundation(Grant No.2022M711623)+3 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20220968)Open Funds for Key Laboratory of Impact and Safety Engineering(Ningbo University)Ministry of Education(Grant No.CJ202201)Open Funds for Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province(Grant No.22kfgk03).
文摘This paper explores the applicability of the generalized wave impedance hypothesis in split Hopkinson pressure bar(SHPB)experiments,particularly under non-ideal conditions.The study investigates the effects of changes in wave impedance ratio and cross-sectional area ratio on the dynamic response of materials at high strain rates.Through theoretical analysis and numerical simulation,the impact of different wave impedance and cross-sectional area ratios on stress wave propagation characteristics is discussed in detail.It is found that when the cross-sections of two bars differ,shear strain occurs at the abrupt cross-section,leading to waveform distortion in the transmitted and reflected waves.The force balance condition does not always align with the momentum conservation theorem,and only when the three waveforms and wavelengths are completely consistent do they align.The research shows that when the wave impedance ratio and cross-sectional area ratio are within a specific range,the generalized wave impedance hypothesis can accurately predict changes in Young’s modulus and density.Additionally,the study extends the exploration to key factors such as wave impedance ratio,wave speed,Young’s modulus,density,and area ratio.
基金supported by the National Key Research and Development Program of China(No.2021YFC3001302)the National Natural Science Foundation of China(No.52274072).
文摘Shearing dislocation is a common failure type for rock–backfill interfaces because of backfill sedimentation and rock strata movement in backfill mining goaf.This paper designed a test method for rock–backfill shearing dislocation.Using digital image techno-logy and three-dimensional(3D)laser morphology scanning techniques,a set of 3D models with rough joint surfaces was established.Further,the mechanical behavior of rock–backfill shearing dislocation was investigated using a direct shear test.The effects of interface roughness on the shear–displacement curve and failure characteristics of rock–backfill specimens were considered.The 3D fractal dimen-sion,profile line joint roughness coefficient(JRC),profile line two-dimensional fractal dimension,and the surface curvature of the frac-tures were obtained.The correlation characterization of surface roughness was then analyzed,and the shear strength could be measured and calculated using JRC.The results showed the following:there were three failure threshold value points in rock–backfill shearing dis-location:30%–50%displacement before the peak,70%–90%displacement before the peak,and 100%displacement before the peak to post-peak,which could be a sign for rock–backfill shearing dislocation failure.The surface JRC could be used to judge the rock–backfill shearing dislocation failure,including post-peak sliding,uniform variations,and gradient change,corresponding to rock–backfill disloca-tion failure on the field site.The research reveals the damage mechanism for rock–backfill complexes based on the free joint surface,fills the gap of existing shearing theoretical systems for isomerism complexes,and provides a theoretical basis for the prevention and control of possible disasters in backfill mining.
文摘This study examines the penetration of 12.7 mm armor piercing incendiary projectiles into SiC ceramic-fiber composite target plates.By observing the recovered projectile and the overall damage morphology of the ceramic-fiber composite target plates.Additionally,multi-level screening and weighing of the recovered projectile and ceramic fragments revealed that the mass distribution of the projectile and ceramic fragments under different backing structures conforms to a powerlaw distribution.Experimental results indicate that for single laminate as the backing,the fragmentation of the projectile and ceramics is highest when T300 is the material.Incorporating a T300 transition layer between the SiC ceramic and aramid fibers(Kevlar)or ultra-high molecular weight polyethylene(UHMWPE)increases the fragmentation of the projectile and ceramics,leading to increased energy absorption.The projectile’s head mainly exhibits pulverized abrasive fragmentation,while larger projectile fragments primarily result from shear and tensile stress-induced shear-tensile failure fractures.The primary damage mode of ceramics under high-speed impact is the expansion of ceramic cones and radial cracks.The main form of damage in UHMWPE laminate is interlayer separation caused by tensile waves,permanent plastic deformation at the back protrusion,and perforation failure primarily due to shear waves.The damage mode of Kevlar laminate is similar to that of UHMWPE,with the distinction being that Kevlar laminate primarily exhibits perforation failure caused by tensile waves.Carbon fiber T300 laminate damage mainly consists of cross-shaped brittle fractures caused by shear waves.
基金supported by the National Natural Science Foundation of China(Grant Nos.12172179,U2341244,and 11772160)。
文摘To enhance the protective performance of ceramic composite armor,ballistic penetration experiments were conducted on Al_(2)O_(3) ceramic-ultra-high molecular weight polyethylene(UHMWPE)composite armor with different thickness configurations.The damage and failure modes of hard projectiles and ceramic-fiber composite targets were analyzed.The recovered projectiles and ceramic fragments were sieved and weighed at multiple stages,revealing a positive correlation between the degree of fragmentation of the projectiles and ceramics and the overall ballistic resistance of the composite targets.Numerical simulations were performed using the LS-DYNA finite element software,and the simulation results showed high consistency with the experimental results,confirming the validity of the material parameters.The results indicate that the projectile heads primarily exhibited crushing and abrasive fragmentation.Larger projectile fragments mainly resulted from tensile and shear stress-induced failure.The failure modes of the composite targets included the formation of ceramic cones and radial cracks under high-velocity impacts.The UHMWPE laminated plates exhibited interlayer separation caused by tensile waves,permanent plastic deformation of the rear surface bulging,and perforation failure primarily due to shear forces.Through extended numerical simulations,while maintaining the same areal density and configuration of9 mm Al_(2)O_(3) ceramic+12 mm UHMWPE laminated composite armor,the thickness configurations of the Al_(2)O_(3) ceramic and UHMWPE laminated backplates were varied,and various thicknesses of UHMWPE laminates were simulated as the cover layer for the ceramic panels.The simulation results indicated that the composite armor configuration of 10 mm Al_(2)O_(3) ceramic+8 mm UHMWPE composite armor increased energy absorption by13.48%.When altering the cover layer thickness,a 4 mm UHMWPE+9 mm Al_(2)O_(3)+8 mm UHMWPE composite armor demonstrated a 27.11%improvement in energy absorption,showing a relatively significant enhancement.
基金supported by MOE(Ministry of Education in China)Project of Humanities and Social Sciences(No.20YJC630022)Shandong Province Natural Science Foundation(No.ZR2017MG033)Fundamental Research Funds for the Central Universities(No.HIT.HSS.201875).
文摘In the era when online shopping economy and online economy increasingly dominate social consumption,WeChat shopping has increasingly become a way that everyone accepts and is willing to try.This study applied Technology Acceptance Model commonly used in the field of information technology and rational behavior theory to the field of consumer behavior,and used the perceived ease of use and perceived usefulness in the technology acceptance model to explain consumers'willingness to use WeChat shopping.At the same time,the moderating effect of consumer innovativeness was also studied.The empirical results show that the main effect of perceived ease of use and usefulness is significant,and the moderating effect of consumer innovativeness is not significant.Based on the research results,the study puts forward the corresponding countermeasures and suggestions.
基金supported by the National Natural Science Foundation of China(Nos.81773725 and 91739102)。
文摘Lipid metabolism disorders contribute to hyperlipidemia and hepatic steatosis.It is ideal to develop drugs simultaneous improving both hyperlipidemia and hepatic steatosis.Nitazoxanide is an FDA-approved oral antiprotozoal drug with excellent pharmacokinetic and safety profile.We found that nitazoxanide and its metabolite tizoxanide induced mild mitochondrial uncoupling and subsequently activated AMPK in Hep G2 cells.Gavage administration of nitazoxanide inhibited high-fat diet(HFD)-induced increases of liver weight,blood and liver lipids,and ameliorated HFD-induced renal lipid accumulation in hamsters.Nitazoxanide significantly improved HFD-induced histopathologic changes of hamster livers.In the hamsters with pre-existing hyperlipidemia and hepatic steatosis,nitazoxanide also showed therapeutic effect.Gavage administration of nitazoxanide improved HFD-induced hepatic steatosis in C57BL/6J mice and western diet(WD)-induced hepatic steatosis in Apoe-/-mice.The present study suggests that repurposing nitazoxanide as a drug for hyperlipidemia and hepatic steatosis treatment is promising.
基金supported by the National Natural Science Foundation of China (Nos. 91739102 and 81773725)
文摘Our previous studies found that mitochondrial uncouplers CCCP and niclosamide inhibited artery constriction and the mechanism involved AMPK activation in vascular smooth muscle cells. BAM15 is a novel type of mitochondrial uncoupler. The aim of the present study is to identify the vasoactivity of BAM15 and characterize the BAM15-induced AMPK activation in vascular smooth muscle cells(A10 cells). BAM15 relaxed phenylephrine(PE)-induced constricted rat mesenteric arteries with intact and denuded endothelium. Pretreatment with BAM15 inhibited PEinduced constriction of rat mesenteric arteries with intact and denuded endothelium. BAM15, CCCP,and niclosamide had the comparable IC50 value of vasorelaxation in PE-induced constriction of rat mesenteric arteries. BAM15 was less cytotoxic in A10 cells compared with CCCP and niclosamide.BAM15 depolarized mitochondrial membrane potential, induced mitochondrial fission, increased mitochondrial ROS production, and increased mitochondrial oxygen consumption rate in A10 cells.BAM15 potently activated AMPK in A10 cells and the efficacy of BAM15 was stronger than that of CCCP, niclosamide, and AMPK positive activators metformin and AICAR. In conclusion, BAM15 activates AMPK in vascular smooth muscle cells with higher potency than that of CCCP, niclosamide and the known AMPK activators metformin and AICAR. The present work indicates that BAM15 is a potent AMPK activator.
文摘In this paper,we study three types of Cantor sets.For any integer m≥4,we show that every real number in[0,k]is the sum of at most k m-th powers of elements in the Cantor ternary set C for some positive integer k,and the smallest such k is 2~m.Moreover,we generalize this result to the middle-1/αCantor set for1<α<2+√5 and m sufficiently large.For the naturally embedded image W of the Cantor dust C×C into the complex plane C,we prove that for any integer m≥3,every element in the closed unit disk in C can be written as the sum of at most 2^(m+8)m-th powers of elements in W.At last,some similar results on p-adic Cantor sets are also obtained.
基金support from the National Natural Science Foundation of China(Grant No.52308095)the National Key Research and Development Program of China(Grant No.2022YFE0197400)the Natural Science Foundation of Hubei Province of China(Grant No.2024AFB586).
文摘As deep borehole heat exchangers(DBHEs)extract heat from geothermal energy with depth of 2–3 kilometers,the circulation water pressure drop is larger than that of shallow-depth borehole heat exchangers,influenced by the water flow rates.This paper conducted field tests and simulation analysis to study the heat transfer performance and water circulation resistance of DBHE in coupled,where the natural circulation characteristic has been discovered and analyzed quantitatively.Results show that the water temperature and density variation along DBHE forms the driving force of natural circulation.For mechanical flow rate of 6.0 kg/s and inlet water temperature of 20.0℃,the natural circulation flow rate reaches about 2.2 kg/s with transient heat extraction power of 78.5 kW,without energy consumption of water pumps.And the larger inlet water temperature,smaller mechanical water flow rate,higher inner tube thermal conductivity coefficient and larger depth of DBHE all contribute to the larger natural circulation water flow rate.In addition,the natural circulation could effectively decrease the comprehensive water pressure drops of DBHE,which is about 47.3%smaller than the calculated value of traditional models.Thus the natural circulation characteristic has significant influence on the heat transfer performance of DBHE,and also on the energy performance of whole heat pump systems.
