Due to the unique deformation characteristics of auxetic materials(Poisson’s ratioμ<0),they have better shock resistance and energy absorption properties than traditional materials.Inspired by the concept of vari...Due to the unique deformation characteristics of auxetic materials(Poisson’s ratioμ<0),they have better shock resistance and energy absorption properties than traditional materials.Inspired by the concept of variable crosssection design,a new auxetic re-entrant honeycomb structure is designed in this study.The detailed design method of re-entrant honeycomb with variable cross-section(VCRH)is provided,and five VCRH structures with the same relative density and different cross-section change rates are proposed.The in-plane impact resistance and energy absorption abilities of VCRH under constant velocity are investigated by ABAQUS/EXPLICIT.The results show that the introduction of variable cross-section design can effectively improve the impact resistance and energy absorption abilities of auxetic re-entrant honeycombs.The VCRH structure has better Young’s modulus,plateau stress,and specific energy absorption(SEA)than traditional re-entrant honeycomb(RH).The influence of microstructure parameters(such as cross-section change rateα)on the dynamic impact performance of VCRH is also studied.Results show that,with the increase in impact velocity andα,the plateau stress and SEA of VCRH increase.A positive correlation is also found between the energy absorption efficiency,impact load uniformity andαunder both medium and high impact speeds.These results can provide a reference for designing improved auxetic re-entrant honeycomb structures.展开更多
This paper presents a simple solution of the dynamic buckling of stiffened plates under in-plane impact loading. Based on large deflection theory, a discretely stiffened plate model has been used. The tangential stres...This paper presents a simple solution of the dynamic buckling of stiffened plates under in-plane impact loading. Based on large deflection theory, a discretely stiffened plate model has been used. The tangential stresses of stiffeners and in-plane displacement are neglected. Appling the Hamilton's principle, the motion equations of stiffened plates are obtained. The deflection of the plate is taken as Fourier series, and using Galerkin method the discrete equations can be deduced, which can be solved easily by Runge-Kutta method. The dynamic buckling loads of the stiffened plates are obtained form Budiansky-Roth criterion.展开更多
The popularization of portable,implantable and wearable microelectronics has greatly stimulated the rapid development of high-power planar micro-supercapacitors(PMSCs).Particularly,the introduction of new functionalit...The popularization of portable,implantable and wearable microelectronics has greatly stimulated the rapid development of high-power planar micro-supercapacitors(PMSCs).Particularly,the introduction of new functionalities(e.g.,high voltage,flexibility,stretchability,self-healing,electrochromism and photo/thermal response)to PMSCs is essential for building multifunctional PMSCs and their smart selfpowered integrated microsystems.In this review,we summarized the latest advances in PMSCs from various functional microdevices to their smart integrated microsystems.Primarily,the functionalities of PMSCs are characterized by three major factors to emphasize their electrochemical behavior and unique scope of application.These include but are not limited to high-voltage outputs(realized through asymmetric configuration,novel electrolyte and modular integration),mechanical resilience that includes various feats of flexibility or stretchability,and response to stimuli(self-healing,electrochromic,photo-responsive,or thermal-responsive properties).Furthermore,three representative integrated microsystems including energy harvester-PMSC,PMSC-energy consumption,and all-in-one selfpowered microsystems are elaborately overviewed to understand the emerging intelligent interaction models.Finally,the key perspectives,challenges and opportunities of PMSCs for powering smart microelectronics are proposed in brief.展开更多
Sheet-metal products are integral parts of engineering industries and academia research. Various testing techniques have revealed the deformation behaviors of sheet metals under complex stress states. Information obta...Sheet-metal products are integral parts of engineering industries and academia research. Various testing techniques have revealed the deformation behaviors of sheet metals under complex stress states. Information obtained from tensile and compression tests, however, are insufficient for the identification of material parameters relevant to modern constitutive laws, which require experimental setups capable of generating various loading conditions and applying great amounts of strain to sheet metals. In-plane shear testing has emerged as an important method to overcome the challenges associated with tension and compression tests and can provide additional information about deformation behaviors under large plastic strains. Materials such as Mg alloys with poor levels of both ductility and formability cannot accommodate large plastic strains. Therefore, tension and compression tests have limitations in explaining the material behaviors that occur during sheet metal forming where large plastic strains are introduced. Many studies have been conducted to explain the deformation behaviors of Mg alloys under shear deformation techniques. These include severe plastic deformation(SPD), especially the equal channel angular pressing(ECAP)and equal channel angular extrusion, rolling combined with shear deformation i.e. differential speed rolling(DSR), and also in-plane shear for sheet metals, particularly under large levels of plastic strain. These in-plane shear technique involves the Miyauchi shear test, ASTM shear test, and twin bridge shear tests. Moreover, many experimental results have revealed that the evolution of microstructure and texture during in-plane shear is closely related to the failure behavior of materials. Therefore, this review is focused on techniques for in-plane shear testing that have been reported thus far, on the effect of in-plane shear on the microstructure development of Mg alloy sheets, and on the usefulness of in-plane shear testing to evaluate the formability of Mg alloy sheets.展开更多
With increasing population and changing demographics,food consumption has experienced a significant transition in quantity and quality.However,a dearth of knowledge remains regarding its environmental impacts and how ...With increasing population and changing demographics,food consumption has experienced a significant transition in quantity and quality.However,a dearth of knowledge remains regarding its environmental impacts and how it responds to demographic dynamics,particularly in emerging economies like China.Using the two-stage Quadratic Almost Demand System(QUAIDS)model,this study empirically examines the impact of demographic dynamics on food consumption and its environmental outcomes based on the provincial data from 2000 to 2020 in China.Under various scenarios,according to changes in demographics,we extend our analysis to project the long-term trend of food consumption and its environmental impacts,including greenhouse gas(GHG)emissions,water footprint(WF),and land appropriation(LA).The results reveal that an increase in the proportion of senior people significantly decreases the consumption of grain and livestock meat and increases the consumption of poultry,egg,and aquatic products,particularly for urban residents.Moreover,an increase in the proportion of males in the population leads to higher consumption of poultry and aquatic products.Correspondingly,in the current scenario of an increased aging population and sex ratio,it is anticipated that GHG emissions,WF,and LA are likely to decrease by 1.37,2.52,and 3.56%,respectively.More importantly,in the scenario adhering to the standards of nutritional intake according to the Dietary Guidelines for Chinese Residents in 2022,GHG emissions,WF,and LA in urban areas would increase by 12.78,20.94,and 18.32%,respectively.Our findings suggest that changing demographics should be considered when designing policies to mitigate the diet-environment-health trilemma and achieve sustainable food consumption.展开更多
Broad-spectrum absorption and highly effective charge-carrier separation are two essential requirements to improve the photocatalytic performance of semiconductor-based photocatalysts.In this work,a fascinating one-ph...Broad-spectrum absorption and highly effective charge-carrier separation are two essential requirements to improve the photocatalytic performance of semiconductor-based photocatalysts.In this work,a fascinating one-photon system is reported by rationally fabricating 2D in-plane Bi_(2)O_(3)/BiOCl(i-Cl)heterostructures for efficient photocatalytic degradation of RhB and TC.Systematic investigations revealed that the matched band structure generated an internal electric field and a chemical bond connection between the Bi_(2)O_(3)and BiOCl in the Bi_(2)O_(3)/BiOCl composite that could effectively improve the utilization ratio of visible light and the separation effectivity of photo-generated carriers in space.The formed interactions at the 2D in-plane heterojunction interface induced the one-photon excitation pathway which has been confirmed by the experiment and DFT calculations.As a result,the i-Cl samples showed significantly enhanced photocatalytic efficiency towards the degradation of RhB and TC(RhB:0.106 min^(-1);TC:0.048 min^(-1))under visible light.The degradation activities of RhB and TC for i-Cl were 265.08 and 4.08times that of pure BiOCl,as well as 9.27 and 2.14 times that of mechanistically mixed Bi_(2)O_(3)/BiOCl samples,respectively.This work provides a logical strategy to construct other 2D in-plane heterojunctions with a one-photon excitation pathway with enhanced performance.展开更多
A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles(RMPs) impacting liquid-filled tanks,and the corresponding hydrodynamic ram(HRAM) was s...A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles(RMPs) impacting liquid-filled tanks,and the corresponding hydrodynamic ram(HRAM) was studied in detail.PTFE/Al/W RMPs with steel-like and aluminum-like densities were prepared by a pressing/sintering process.The projectiles impacted a liquid-filled steel tank with front aluminum panel at approximately 1250 m/s.The corresponding cavity evolution characteristics and HRAM pressure were recorded by high-speed camera and pressure acquisition system,and further compared to those of steel and aluminum projectiles.Significantly different from the conical cavity formed by the inert metal projectile,the cavity formed by the RMP appeared as an ellipsoid with a conical front.The RMPs were demonstrated to enhance the radial growth velocity of cavity,the global HRAM pressure amplitude and the front panel damage,indicating the enhanced HRAM and structural damage behavior.Furthermore,combining the impact-induced fragmentation and deflagration characteristics,the cavity evolution of RMPs under the combined effect of kinetic energy impact and chemical energy release was analyzed.The mechanism of enhanced HRAM pressure induced by the RMPs was further revealed based on the theoretical model of the initial impact wave and the impulse analysis.Finally,the linear correlation between the deformation-thickness ratio and the non-dimensional impulse for the front panel was obtained and analyzed.It was determined that the enhanced near-field impulse induced by the RMPs was the dominant reason for the enhanced structural damage behavior.展开更多
This paper deals with the collision of sphere shape grenades with sand media.The central issue of the article is the establishing of an empirical velocity equation of the grenade while impacting on sand that is used t...This paper deals with the collision of sphere shape grenades with sand media.The central issue of the article is the establishing of an empirical velocity equation of the grenade while impacting on sand that is used to solve motion equations of the mechanical mechanism inside the impact grenade fuze.The paper focuses on impact velocities that are lower than 5 m s^(-1).An experiment was conducted to study the velocity of the grenade while impacting on dry sand.A high-speed camera video was used to capture the grenade positions.The grenade velocity in the impact process was generated from these video data.Some types of fitting curves are used to regress the velocity equation of the grenade while interacting with the sand media and the best-fitting model is chosen.The result shows the regression curve has a high correlation with the experiment data for grenade velocities below 5 m s^(-1).The received regression equation is useful for analyzing the working ability of the inertial mechanism inside the impact grenade or analyzing and choosing the appropriate parameters of each part in the inertial mechanism to meet the required characteristics of the mechanism.展开更多
Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture process.In this study,the trade-off relationship between the...Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture process.In this study,the trade-off relationship between the strength and toughness of a DZ2 axle steel at various tempering temperatures and the cause of the improvement in impact toughness was evaluated.The tempering process dramatically influenced carbide precipitation behavior,which resulted in different aspect ratios of carbides.Impact toughness improved along with the rise in tempering temperature mainly due to the increase in energy required in impact crack propagation.The characteristics of the impact crack propagation process were studied through a comprehensive analysis of stress distribution,oscilloscopic impact statistics,fracture morphology,and carbide morphology.The poor impact toughness of low-tempering-temperature specimens was attributed to the increased number of stress concentration points caused by carbide morphology in the small plastic zone during the propagation process,which resulted in a mixed distribution of brittle and ductile fractures on the fracture surface.展开更多
This work presents a novel approach to the dynamic response analysis of a Euler-Bernoulli beam resting on a Winkler soil model and subjected to an impact loading.The approach considers that damping has much less impor...This work presents a novel approach to the dynamic response analysis of a Euler-Bernoulli beam resting on a Winkler soil model and subjected to an impact loading.The approach considers that damping has much less importance in controlling the maximum response to impulsive loadings because the maximum response is reached in a very short time,before the damping forces can dissipate a significant portion of the energy input into the system.The development of two sine series solutions,relating to different types of impulsive loadings,one involving a single concentrated force and the other a distributed line load,are presented.This study revealed that when a simply supported Euler-Bernoulli beam,resting on a Winkler soil model,is subject to an impact load,the resulting vertical displacements,bending moments and shear forces produced along the span of the beam are considerably affected.In particular,the quantification of this effect is best observed,relative to the corresponding static solution,via an amplification factor.The computed impact amplification factors,for the sub-grade moduli used in this study,were in magnitude greater than 2,thus confirming the multiple-degree-of-freedom nature of the problem.展开更多
The current research of Charpy impact mainly focuses on obtaining the ductile brittle transition temperature of materials by experiments.Compared with experiments,numerical simulation can study many problems with hars...The current research of Charpy impact mainly focuses on obtaining the ductile brittle transition temperature of materials by experiments.Compared with experiments,numerical simulation can study many problems with harsh conditions.However,there are still few studies on the influence of geometric factors such as side grooves.In this paper,the geometry of standard Charpy impact test is designed.Specimens with different widths and side grooves are tested.The finite element model of Charpy impact was established by ABAQUS software.Use test results and simulation results to verify each other.The effects of sample width,side groove depth and side groove bottom fillet on the impact fracture resistance of the sample were studied.The results show that the specimen width is positively correlated with the impact toughness of the specimen.The side groove greatly reduces the impact toughness of the material;the toughness of side groove decreases with the increase of depth;the fracture toughness of side groove decreases with the increase of fillet at the bottom of side groove.The proportion of toughness energy to impact energy of samples was analyzed.The results show that the toughness energy accounts for about 70%of the impact energy of the sample,which has little to do with the geometric characteristics of the sample.This study presents a reliable method for studying Charpy impact tests.The influence of geometric parameters is obtained,which provides a reference method for the study of impact toughness of high toughness materials.展开更多
The effects of projectile/target impedance matching and projectile shape on energy,momentum transfer and projectile melting during collisions are investigated by numerical simulation.By comparing the computation resul...The effects of projectile/target impedance matching and projectile shape on energy,momentum transfer and projectile melting during collisions are investigated by numerical simulation.By comparing the computation results with the experimental results,the correctness of the calculation and the statistical method of momentum transfer coefficient is verified.Different shapes of aluminum,copper and heavy tungsten alloy projectiles striking aluminum,basalt,and pumice target for impacts up to 10 km/s are simulated.The influence mechanism of the shape of the projectile and projectile/target density on the momentum transfer was obtained.With an increase in projectile density and length-diameter ratio,the energy transfer time between the projectile and targets is prolonged.The projectile decelerates slowly,resulting in a larger cratering depth.The energy consumed by the projectile in the excavation stage increased,resulting in lower mass-velocity of ejecta and momentum transfer coefficient.The numerical simulation results demonstrated that for different projectile/target combinations,the higher the wave impedance of the projectile,the higher the initial phase transition velocity and the smaller the mass of phase transition.The results can provide theoretical guidance for kinetic impactor design and material selection.展开更多
Impact engineering encompasses many events of our lives.Examples include vehicle collisions,catastrophic collapse of infrastructures from explosion,ballistic impact of armour,hitting cricket balls in sports,falling of...Impact engineering encompasses many events of our lives.Examples include vehicle collisions,catastrophic collapse of infrastructures from explosion,ballistic impact of armour,hitting cricket balls in sports,falling off a bicycle.In such an event,an engineer needs to understand and quantify complex issues like identifying the impact loadings,obtaining material properties at high strain rates and evaluating structural responses and consequences.This engineering field receives great interests from industry and the research community.Several monographs have been published over the decades and related journals,such as the International Journal of Impact Engineering and Defence Technology,have been established and disseminate the latest research findings.展开更多
A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combin...A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.展开更多
Purpose:The disseminating of academic knowledge to nonacademic audiences partly relies on the transition of subsequent citing papers.This study aims to investigate direct and indirect impact on technology and policy o...Purpose:The disseminating of academic knowledge to nonacademic audiences partly relies on the transition of subsequent citing papers.This study aims to investigate direct and indirect impact on technology and policy originating from transformative research based on ego citation network.Design/methodology/approach:Key Nobel Prize-winning publications(NPs)in fields of gene engineering and astrophysics are regarded as a proxy for transformative research.In this contribution,we introduce a network-structural indicator of citing patents to measure technological impact of a target article and use policy citations as a preliminary tool for policy impact.Findings:The results show that the impact on technology and policy of NPs are higher than that of their subsequent citation generations in gene engineering but not in astrophysics.Research limitations:The selection of Nobel Prizes is not balanced and the database used in this study,Dimensions,suffers from incompleteness and inaccuracy of citation links.Practical implications:Our findings provide useful clues to better understand the characteristics of transformative research in technological and policy impact.Originality/value:This study proposes a new framework to explore the direct and indirect impact on technology and policy originating from transformative research.展开更多
Pregnancy comes with a combination of physical changes and physiological immunosuppression that increases the susceptibility of women to pathogens and in turn,rises the prevalence of infectious diseases.
Introduction: Seasonal Malaria Chemoprevention (SMC) aims at preventing malaria in children during the high transmission season. It has been recommended by the WHO since 2013 for children from the age of 3-59 months. ...Introduction: Seasonal Malaria Chemoprevention (SMC) aims at preventing malaria in children during the high transmission season. It has been recommended by the WHO since 2013 for children from the age of 3-59 months. However, despite the impact of this intervention, a peak in the prevalence and incidence of malaria is observed in children from the age of 5-9 years. The aim of this study is to determine from the current literature the feasibility, impact and cost-effectiveness of extending SMC to five cycles and to older children. Methods: A litterature search of PubMed/Medline, NCBI and Google scholar identified 1333 articles. After reading the titles and abstracts by two authors, 24 articles were selected and submitted for full reading. Random control studies on the extension of SMC, malaria, feasibility of SMC, impact of SMC and cost-effectiveness of SMC were selected. A total of 16 articles were included for the qualitative synthesis after excluding 8 studies. Results: Following the summary of the evidence, we conclude that the extension is feasible but will be confronted with the unavailability of older children. The intervention period coincides with field work. SMC is effective in reducing the prevalence and incidence of malaria and the parasite density in children. The financial cost of administering SMC is lower than that of treating a child suffering from malaria. Conclusion: After analysing the information, it was found that the majority of the African population supports the extension of the SMC to the number of cycles and the age group in order to alleviate the high mortality and morbidity rates among children due to malaria.展开更多
1 A new type of impact factor The Unique citing documents Journal Impact Factor(Uniq-JIF)is defined as follows:Uniq-JIF=Number of unique citing documents/Number of citable items(1)We note that formula(1)is given in a ...1 A new type of impact factor The Unique citing documents Journal Impact Factor(Uniq-JIF)is defined as follows:Uniq-JIF=Number of unique citing documents/Number of citable items(1)We note that formula(1)is given in a generic form.In concrete applications,one must state the publication for which the Uniq-JIF is calculated(a journal,an edited book,a conference proceedings).展开更多
Cardiovascular disease remains the leading cause of mortality in women,yet it has not raised the awareness from the public.The pathogenesis of cardiovascular disease differs significantly between females and males con...Cardiovascular disease remains the leading cause of mortality in women,yet it has not raised the awareness from the public.The pathogenesis of cardiovascular disease differs significantly between females and males concerning the effect of sex hormones.Estrogen and progestogen impact cardiovascular system through genomic and non-genomic effects.Before menopause,cardiovascular protective effects of estrogens have been well described.Progestogens were often used in combination with estrogens in hormone therapy.Fluctuations in sex hormone levels,particularly estrogen deficiency,were considered the specific risk factor in women’s cardiovascular disease.However,considerable heterogeneity in the impact of hormone therapy was observed in clinical trials.The heterogeneity is likely closely associated with factors such as the initial time,administration route,dosage,and formulation of hormone therapy.This review will delve into the pathogenesis and hormone therapy,summarizing the effect of female sex hormones on hypertension,pre-eclampsia,coronary heart disease,heart failure with preserved ejection fraction,and cardiovascular risk factors specific to women.展开更多
基金This research is supported by the National Natural Science Foundation of China(No.11902232).
文摘Due to the unique deformation characteristics of auxetic materials(Poisson’s ratioμ<0),they have better shock resistance and energy absorption properties than traditional materials.Inspired by the concept of variable crosssection design,a new auxetic re-entrant honeycomb structure is designed in this study.The detailed design method of re-entrant honeycomb with variable cross-section(VCRH)is provided,and five VCRH structures with the same relative density and different cross-section change rates are proposed.The in-plane impact resistance and energy absorption abilities of VCRH under constant velocity are investigated by ABAQUS/EXPLICIT.The results show that the introduction of variable cross-section design can effectively improve the impact resistance and energy absorption abilities of auxetic re-entrant honeycombs.The VCRH structure has better Young’s modulus,plateau stress,and specific energy absorption(SEA)than traditional re-entrant honeycomb(RH).The influence of microstructure parameters(such as cross-section change rateα)on the dynamic impact performance of VCRH is also studied.Results show that,with the increase in impact velocity andα,the plateau stress and SEA of VCRH increase.A positive correlation is also found between the energy absorption efficiency,impact load uniformity andαunder both medium and high impact speeds.These results can provide a reference for designing improved auxetic re-entrant honeycomb structures.
文摘This paper presents a simple solution of the dynamic buckling of stiffened plates under in-plane impact loading. Based on large deflection theory, a discretely stiffened plate model has been used. The tangential stresses of stiffeners and in-plane displacement are neglected. Appling the Hamilton's principle, the motion equations of stiffened plates are obtained. The deflection of the plate is taken as Fourier series, and using Galerkin method the discrete equations can be deduced, which can be solved easily by Runge-Kutta method. The dynamic buckling loads of the stiffened plates are obtained form Budiansky-Roth criterion.
基金the National Natural Science Foundation of China,China (Grant Nos.22125903,51872283,22109040)the“Transformational Technologies for Clean Energy and Demonstration”Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDA21000000)+4 种基金the Dalian Innovation Support Plan for High Level Talents,China (2019RT09)DICP,China (DICP I202032)the Dalian National Laboratory For Clean Energy (DNL),CAS,DNL Cooperation Fund,CAS,China (DNL202016,DNL202019)the Top-Notch Talent Program of Henan Agricultural University,China (30500947)the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy,China (YLU-DNL Fund 2021002,YLU-DNL Fund 2021009)。
文摘The popularization of portable,implantable and wearable microelectronics has greatly stimulated the rapid development of high-power planar micro-supercapacitors(PMSCs).Particularly,the introduction of new functionalities(e.g.,high voltage,flexibility,stretchability,self-healing,electrochromism and photo/thermal response)to PMSCs is essential for building multifunctional PMSCs and their smart selfpowered integrated microsystems.In this review,we summarized the latest advances in PMSCs from various functional microdevices to their smart integrated microsystems.Primarily,the functionalities of PMSCs are characterized by three major factors to emphasize their electrochemical behavior and unique scope of application.These include but are not limited to high-voltage outputs(realized through asymmetric configuration,novel electrolyte and modular integration),mechanical resilience that includes various feats of flexibility or stretchability,and response to stimuli(self-healing,electrochromic,photo-responsive,or thermal-responsive properties).Furthermore,three representative integrated microsystems including energy harvester-PMSC,PMSC-energy consumption,and all-in-one selfpowered microsystems are elaborately overviewed to understand the emerging intelligent interaction models.Finally,the key perspectives,challenges and opportunities of PMSCs for powering smart microelectronics are proposed in brief.
基金financially supported by the Science and Engineering Research Board (SERB)a statutory body of the Department of Science&Technology (DST)+1 种基金Government of India through the Start-up Research Grant (SRG) scheme (File No. SRG/2020/000341)National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT)(NRF-2020R1A2C1010134)。
文摘Sheet-metal products are integral parts of engineering industries and academia research. Various testing techniques have revealed the deformation behaviors of sheet metals under complex stress states. Information obtained from tensile and compression tests, however, are insufficient for the identification of material parameters relevant to modern constitutive laws, which require experimental setups capable of generating various loading conditions and applying great amounts of strain to sheet metals. In-plane shear testing has emerged as an important method to overcome the challenges associated with tension and compression tests and can provide additional information about deformation behaviors under large plastic strains. Materials such as Mg alloys with poor levels of both ductility and formability cannot accommodate large plastic strains. Therefore, tension and compression tests have limitations in explaining the material behaviors that occur during sheet metal forming where large plastic strains are introduced. Many studies have been conducted to explain the deformation behaviors of Mg alloys under shear deformation techniques. These include severe plastic deformation(SPD), especially the equal channel angular pressing(ECAP)and equal channel angular extrusion, rolling combined with shear deformation i.e. differential speed rolling(DSR), and also in-plane shear for sheet metals, particularly under large levels of plastic strain. These in-plane shear technique involves the Miyauchi shear test, ASTM shear test, and twin bridge shear tests. Moreover, many experimental results have revealed that the evolution of microstructure and texture during in-plane shear is closely related to the failure behavior of materials. Therefore, this review is focused on techniques for in-plane shear testing that have been reported thus far, on the effect of in-plane shear on the microstructure development of Mg alloy sheets, and on the usefulness of in-plane shear testing to evaluate the formability of Mg alloy sheets.
基金This work was supported by the Qinchuangyuan Project of Shaanxi Province,China(QCYRCXM-2022-145)the Major Project of the Key Research Base of Humanities and Social Sciences of the Ministry of Education,China(22JJD790052)+1 种基金the Chinese Universities Scientific Fund(Z1010422003)the National Natural Science Foundation of China(72373117).
文摘With increasing population and changing demographics,food consumption has experienced a significant transition in quantity and quality.However,a dearth of knowledge remains regarding its environmental impacts and how it responds to demographic dynamics,particularly in emerging economies like China.Using the two-stage Quadratic Almost Demand System(QUAIDS)model,this study empirically examines the impact of demographic dynamics on food consumption and its environmental outcomes based on the provincial data from 2000 to 2020 in China.Under various scenarios,according to changes in demographics,we extend our analysis to project the long-term trend of food consumption and its environmental impacts,including greenhouse gas(GHG)emissions,water footprint(WF),and land appropriation(LA).The results reveal that an increase in the proportion of senior people significantly decreases the consumption of grain and livestock meat and increases the consumption of poultry,egg,and aquatic products,particularly for urban residents.Moreover,an increase in the proportion of males in the population leads to higher consumption of poultry and aquatic products.Correspondingly,in the current scenario of an increased aging population and sex ratio,it is anticipated that GHG emissions,WF,and LA are likely to decrease by 1.37,2.52,and 3.56%,respectively.More importantly,in the scenario adhering to the standards of nutritional intake according to the Dietary Guidelines for Chinese Residents in 2022,GHG emissions,WF,and LA in urban areas would increase by 12.78,20.94,and 18.32%,respectively.Our findings suggest that changing demographics should be considered when designing policies to mitigate the diet-environment-health trilemma and achieve sustainable food consumption.
基金supported by the National Natural Science Foundation of China(11874314,12174157,and 12074150)the Natural Science Foundation of Jiangsu Province(BK20201424)+1 种基金the Modern Agricultural Equipment and Technology Collaborative Innovation Project(XTCX2025)the Graduate Research and Innovation Projects of Jiangsu Province(KYCX22_3602)。
文摘Broad-spectrum absorption and highly effective charge-carrier separation are two essential requirements to improve the photocatalytic performance of semiconductor-based photocatalysts.In this work,a fascinating one-photon system is reported by rationally fabricating 2D in-plane Bi_(2)O_(3)/BiOCl(i-Cl)heterostructures for efficient photocatalytic degradation of RhB and TC.Systematic investigations revealed that the matched band structure generated an internal electric field and a chemical bond connection between the Bi_(2)O_(3)and BiOCl in the Bi_(2)O_(3)/BiOCl composite that could effectively improve the utilization ratio of visible light and the separation effectivity of photo-generated carriers in space.The formed interactions at the 2D in-plane heterojunction interface induced the one-photon excitation pathway which has been confirmed by the experiment and DFT calculations.As a result,the i-Cl samples showed significantly enhanced photocatalytic efficiency towards the degradation of RhB and TC(RhB:0.106 min^(-1);TC:0.048 min^(-1))under visible light.The degradation activities of RhB and TC for i-Cl were 265.08 and 4.08times that of pure BiOCl,as well as 9.27 and 2.14 times that of mechanistically mixed Bi_(2)O_(3)/BiOCl samples,respectively.This work provides a logical strategy to construct other 2D in-plane heterojunctions with a one-photon excitation pathway with enhanced performance.
基金supported by the Youth Foundation of State Key Laboratory of Explosion Science and Technology (Grant No.QNKT22-12)the State Key Program of National Natural Science Foundation of China (Grant No.12132003)。
文摘A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles(RMPs) impacting liquid-filled tanks,and the corresponding hydrodynamic ram(HRAM) was studied in detail.PTFE/Al/W RMPs with steel-like and aluminum-like densities were prepared by a pressing/sintering process.The projectiles impacted a liquid-filled steel tank with front aluminum panel at approximately 1250 m/s.The corresponding cavity evolution characteristics and HRAM pressure were recorded by high-speed camera and pressure acquisition system,and further compared to those of steel and aluminum projectiles.Significantly different from the conical cavity formed by the inert metal projectile,the cavity formed by the RMP appeared as an ellipsoid with a conical front.The RMPs were demonstrated to enhance the radial growth velocity of cavity,the global HRAM pressure amplitude and the front panel damage,indicating the enhanced HRAM and structural damage behavior.Furthermore,combining the impact-induced fragmentation and deflagration characteristics,the cavity evolution of RMPs under the combined effect of kinetic energy impact and chemical energy release was analyzed.The mechanism of enhanced HRAM pressure induced by the RMPs was further revealed based on the theoretical model of the initial impact wave and the impulse analysis.Finally,the linear correlation between the deformation-thickness ratio and the non-dimensional impulse for the front panel was obtained and analyzed.It was determined that the enhanced near-field impulse induced by the RMPs was the dominant reason for the enhanced structural damage behavior.
基金supported by the research project of the University of Defence in Brno DZRO-FVT22-VAROPS。
文摘This paper deals with the collision of sphere shape grenades with sand media.The central issue of the article is the establishing of an empirical velocity equation of the grenade while impacting on sand that is used to solve motion equations of the mechanical mechanism inside the impact grenade fuze.The paper focuses on impact velocities that are lower than 5 m s^(-1).An experiment was conducted to study the velocity of the grenade while impacting on dry sand.A high-speed camera video was used to capture the grenade positions.The grenade velocity in the impact process was generated from these video data.Some types of fitting curves are used to regress the velocity equation of the grenade while interacting with the sand media and the best-fitting model is chosen.The result shows the regression curve has a high correlation with the experiment data for grenade velocities below 5 m s^(-1).The received regression equation is useful for analyzing the working ability of the inertial mechanism inside the impact grenade or analyzing and choosing the appropriate parameters of each part in the inertial mechanism to meet the required characteristics of the mechanism.
基金the National Natural Science Foundation of China(Nos.52001310 and 52130002)the National Science and Technology Major Project(No.J2019-VI-0019-0134)+1 种基金KC Wong Education Foundation(No.GJTD-2020-09)Institute of Metal Res earch Innovation Fund(No.2023-ZD01)。
文摘Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture process.In this study,the trade-off relationship between the strength and toughness of a DZ2 axle steel at various tempering temperatures and the cause of the improvement in impact toughness was evaluated.The tempering process dramatically influenced carbide precipitation behavior,which resulted in different aspect ratios of carbides.Impact toughness improved along with the rise in tempering temperature mainly due to the increase in energy required in impact crack propagation.The characteristics of the impact crack propagation process were studied through a comprehensive analysis of stress distribution,oscilloscopic impact statistics,fracture morphology,and carbide morphology.The poor impact toughness of low-tempering-temperature specimens was attributed to the increased number of stress concentration points caused by carbide morphology in the small plastic zone during the propagation process,which resulted in a mixed distribution of brittle and ductile fractures on the fracture surface.
基金l’UniversitéLaval for the financial support of his sabbatical year at Dipartimento di Bioscienze e Territorio,Universitàdegli Studi del Molise in Campobasso,Italy。
文摘This work presents a novel approach to the dynamic response analysis of a Euler-Bernoulli beam resting on a Winkler soil model and subjected to an impact loading.The approach considers that damping has much less importance in controlling the maximum response to impulsive loadings because the maximum response is reached in a very short time,before the damping forces can dissipate a significant portion of the energy input into the system.The development of two sine series solutions,relating to different types of impulsive loadings,one involving a single concentrated force and the other a distributed line load,are presented.This study revealed that when a simply supported Euler-Bernoulli beam,resting on a Winkler soil model,is subject to an impact load,the resulting vertical displacements,bending moments and shear forces produced along the span of the beam are considerably affected.In particular,the quantification of this effect is best observed,relative to the corresponding static solution,via an amplification factor.The computed impact amplification factors,for the sub-grade moduli used in this study,were in magnitude greater than 2,thus confirming the multiple-degree-of-freedom nature of the problem.
基金Supported by National Natural Science Foundation of China(Grant Nos.51975526,51505425)National Key R&D Program of China(Grant No.2018YFC0808800)+1 种基金Open Project of Key Laboratory of MEM of China(Grant No.2020XFZB10)Technical Service Projects(Grant Nos.HZFS-XZ-2022-07-02,XJBY-20211221).
文摘The current research of Charpy impact mainly focuses on obtaining the ductile brittle transition temperature of materials by experiments.Compared with experiments,numerical simulation can study many problems with harsh conditions.However,there are still few studies on the influence of geometric factors such as side grooves.In this paper,the geometry of standard Charpy impact test is designed.Specimens with different widths and side grooves are tested.The finite element model of Charpy impact was established by ABAQUS software.Use test results and simulation results to verify each other.The effects of sample width,side groove depth and side groove bottom fillet on the impact fracture resistance of the sample were studied.The results show that the specimen width is positively correlated with the impact toughness of the specimen.The side groove greatly reduces the impact toughness of the material;the toughness of side groove decreases with the increase of depth;the fracture toughness of side groove decreases with the increase of fillet at the bottom of side groove.The proportion of toughness energy to impact energy of samples was analyzed.The results show that the toughness energy accounts for about 70%of the impact energy of the sample,which has little to do with the geometric characteristics of the sample.This study presents a reliable method for studying Charpy impact tests.The influence of geometric parameters is obtained,which provides a reference method for the study of impact toughness of high toughness materials.
基金the National Natural Science Foundation of China(Grant Nos.62227901,12202068)the Civil Aerospace Pre-research Project(Grant No.D020304).
文摘The effects of projectile/target impedance matching and projectile shape on energy,momentum transfer and projectile melting during collisions are investigated by numerical simulation.By comparing the computation results with the experimental results,the correctness of the calculation and the statistical method of momentum transfer coefficient is verified.Different shapes of aluminum,copper and heavy tungsten alloy projectiles striking aluminum,basalt,and pumice target for impacts up to 10 km/s are simulated.The influence mechanism of the shape of the projectile and projectile/target density on the momentum transfer was obtained.With an increase in projectile density and length-diameter ratio,the energy transfer time between the projectile and targets is prolonged.The projectile decelerates slowly,resulting in a larger cratering depth.The energy consumed by the projectile in the excavation stage increased,resulting in lower mass-velocity of ejecta and momentum transfer coefficient.The numerical simulation results demonstrated that for different projectile/target combinations,the higher the wave impedance of the projectile,the higher the initial phase transition velocity and the smaller the mass of phase transition.The results can provide theoretical guidance for kinetic impactor design and material selection.
文摘Impact engineering encompasses many events of our lives.Examples include vehicle collisions,catastrophic collapse of infrastructures from explosion,ballistic impact of armour,hitting cricket balls in sports,falling off a bicycle.In such an event,an engineer needs to understand and quantify complex issues like identifying the impact loadings,obtaining material properties at high strain rates and evaluating structural responses and consequences.This engineering field receives great interests from industry and the research community.Several monographs have been published over the decades and related journals,such as the International Journal of Impact Engineering and Defence Technology,have been established and disseminate the latest research findings.
文摘A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.
基金supported by the National Natural Science Foundation of China(Grant No.71974167).
文摘Purpose:The disseminating of academic knowledge to nonacademic audiences partly relies on the transition of subsequent citing papers.This study aims to investigate direct and indirect impact on technology and policy originating from transformative research based on ego citation network.Design/methodology/approach:Key Nobel Prize-winning publications(NPs)in fields of gene engineering and astrophysics are regarded as a proxy for transformative research.In this contribution,we introduce a network-structural indicator of citing patents to measure technological impact of a target article and use policy citations as a preliminary tool for policy impact.Findings:The results show that the impact on technology and policy of NPs are higher than that of their subsequent citation generations in gene engineering but not in astrophysics.Research limitations:The selection of Nobel Prizes is not balanced and the database used in this study,Dimensions,suffers from incompleteness and inaccuracy of citation links.Practical implications:Our findings provide useful clues to better understand the characteristics of transformative research in technological and policy impact.Originality/value:This study proposes a new framework to explore the direct and indirect impact on technology and policy originating from transformative research.
基金supported by Dirección General del Personal Académico(DGAPA)PAPIIT IN207123,UNAM(to AZ)。
文摘Pregnancy comes with a combination of physical changes and physiological immunosuppression that increases the susceptibility of women to pathogens and in turn,rises the prevalence of infectious diseases.
文摘Introduction: Seasonal Malaria Chemoprevention (SMC) aims at preventing malaria in children during the high transmission season. It has been recommended by the WHO since 2013 for children from the age of 3-59 months. However, despite the impact of this intervention, a peak in the prevalence and incidence of malaria is observed in children from the age of 5-9 years. The aim of this study is to determine from the current literature the feasibility, impact and cost-effectiveness of extending SMC to five cycles and to older children. Methods: A litterature search of PubMed/Medline, NCBI and Google scholar identified 1333 articles. After reading the titles and abstracts by two authors, 24 articles were selected and submitted for full reading. Random control studies on the extension of SMC, malaria, feasibility of SMC, impact of SMC and cost-effectiveness of SMC were selected. A total of 16 articles were included for the qualitative synthesis after excluding 8 studies. Results: Following the summary of the evidence, we conclude that the extension is feasible but will be confronted with the unavailability of older children. The intervention period coincides with field work. SMC is effective in reducing the prevalence and incidence of malaria and the parasite density in children. The financial cost of administering SMC is lower than that of treating a child suffering from malaria. Conclusion: After analysing the information, it was found that the majority of the African population supports the extension of the SMC to the number of cycles and the age group in order to alleviate the high mortality and morbidity rates among children due to malaria.
文摘1 A new type of impact factor The Unique citing documents Journal Impact Factor(Uniq-JIF)is defined as follows:Uniq-JIF=Number of unique citing documents/Number of citable items(1)We note that formula(1)is given in a generic form.In concrete applications,one must state the publication for which the Uniq-JIF is calculated(a journal,an edited book,a conference proceedings).
基金supported by the National Key Research and Development Program of China (No.2022YFC-3602500)
文摘Cardiovascular disease remains the leading cause of mortality in women,yet it has not raised the awareness from the public.The pathogenesis of cardiovascular disease differs significantly between females and males concerning the effect of sex hormones.Estrogen and progestogen impact cardiovascular system through genomic and non-genomic effects.Before menopause,cardiovascular protective effects of estrogens have been well described.Progestogens were often used in combination with estrogens in hormone therapy.Fluctuations in sex hormone levels,particularly estrogen deficiency,were considered the specific risk factor in women’s cardiovascular disease.However,considerable heterogeneity in the impact of hormone therapy was observed in clinical trials.The heterogeneity is likely closely associated with factors such as the initial time,administration route,dosage,and formulation of hormone therapy.This review will delve into the pathogenesis and hormone therapy,summarizing the effect of female sex hormones on hypertension,pre-eclampsia,coronary heart disease,heart failure with preserved ejection fraction,and cardiovascular risk factors specific to women.