Based on energy equilibrium,a new procedure called the Membrane Factor Method is devel- oped to analyze the dynamic plastic response of plates with deflections in the range where both bending mo- ments and membrane fo...Based on energy equilibrium,a new procedure called the Membrane Factor Method is devel- oped to analyze the dynamic plastic response of plates with deflections in the range where both bending mo- ments and membrane forces are important.The final deflection of a simply -supported circular rigid-plastic plate loaded by a uniformly distributed impulse is obtained.In comparison with other approximate solutions, the present results are found to be simpler and in better agreement with the corresponding experimental values reoorded by Florence.展开更多
Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is complicated by their discontinuity and inhomogeneity. The finite element method (FEM) and the finite strip method are...Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is complicated by their discontinuity and inhomogeneity. The finite element method (FEM) and the finite strip method are usually adopted in their analysis. Although many useful conclusions have been obtained, the computational cost is enormous. Based on some assumptions, the dynamic plastic response of clamped stiffened plates with large deflections was theoretically investigated herein by a singly symmetric beam model. Firstly, the deflection conditions that a plastic string must satisfy were obtained by the linearized moment-axial force interaction curve for singly symmetric cross sections and the associated plastic flow rule. Secondly, the possible motion mechanisms of the beam under different load intensity were analysed in detail. For structures with plastic deformations, a simplified method was then given that the arbitrary impact load can be replaced equivalently by a rectangular pulse. Finally, to confirm the validity of the proposed method, the dynamic plastic response of a one-way stiffened plate with four fully clamped edges was calculated. The theoretical results were in good agreement with those of FEM. It indicates that the present calculation model is easy and feasible, and the equivalent substitution of load almost has no influence on the final deflection.展开更多
This paper concerns the dynamic plastic response of a circular plate resting on fluid subjected to a uniformly distributed rectangular load pulse with finite deformation. It is assumed that the fluid is incompressible...This paper concerns the dynamic plastic response of a circular plate resting on fluid subjected to a uniformly distributed rectangular load pulse with finite deformation. It is assumed that the fluid is incompressible and inviscous, and the plate is made of rigid-plastic material and simply supported along its edge. By using the method of the Hankel integral transformation, the nonuniform fluid resistance is derived as the plate and the fluid is coupled. Finally, an analytic solution for a circular plate under a medium load is obtained according to the equations of motion of the plate with finite deformation.展开更多
The large deflection dynamic plastic response of fully clamped square plates with stiffeners under blast load is analyzed in detail in this paper. Various relevant motion patterns and criterions are presented. The for...The large deflection dynamic plastic response of fully clamped square plates with stiffeners under blast load is analyzed in detail in this paper. Various relevant motion patterns and criterions are presented. The formulas of maximum permanent deformation of the plates with stiffeners are derived. The results of calculation are compared with those of experiment in [3], with good agreement shown in most cases.展开更多
In this paper the problem of a circular beam subjected to radial impact by a rigid mass at its lip in its own plane is investigaleil on the basis of rigid-perfectly plastic assumption. The analytical solution of the p...In this paper the problem of a circular beam subjected to radial impact by a rigid mass at its lip in its own plane is investigaleil on the basis of rigid-perfectly plastic assumption. The analytical solution of the particle velocities is obtained as the junction of travelling plastic hinge location. Ky analysing the solution, some special properties oj circular beam problem are found.展开更多
The rigid, perfectly plastic dynamic response of a free-free beam subjected to impact by a projectile at any cross-section is studied. The instantaneous deformations of the beam are given through an analysis of the ...The rigid, perfectly plastic dynamic response of a free-free beam subjected to impact by a projectile at any cross-section is studied. The instantaneous deformations of the beam are given through an analysis of the complete solution for rigid plastic structures. The in?uence of some parameters such as the input energy and mass ratio on the plastic deformation, travelling plastic hinge position and energy partitioning of the beam are discussed.展开更多
Aim To analyze dynamic failure of aerospace strutures subjected lateral impulsive loading. Methods Structures were modeled as rigid-perfectly plastic free-free stepped beams. Basic equations of motion un set up f...Aim To analyze dynamic failure of aerospace strutures subjected lateral impulsive loading. Methods Structures were modeled as rigid-perfectly plastic free-free stepped beams. Basic equations of motion un set up for analysis. Results Final pat deformation and rigid motion solutions were determined for a uniform impulsive loading. The critical rupture conditions for a space shuttle and a missile were obtained. Conclusion Failure is possible for aerospace structures under a uniform impulsive loading, but it is mere difficult in space.展开更多
A theoretical analysis is presented for the dynamic plastic behavior of a simply supported rigid, perfectly plastic circular plate in damping medium with finite-deflections subjected to a rectangular pressure pulse. A...A theoretical analysis is presented for the dynamic plastic behavior of a simply supported rigid, perfectly plastic circular plate in damping medium with finite-deflections subjected to a rectangular pressure pulse. Analytical solutions of every moving stage under both medium and high loads are developed.展开更多
Aims Changes in the phenotype of crops(phenotypic plasticity)are known to play an important role in determining responses to nutrient availability,with the direction and magnitude of plasticity of individual traits be...Aims Changes in the phenotype of crops(phenotypic plasticity)are known to play an important role in determining responses to nutrient availability,with the direction and magnitude of plasticity of individual traits being crucial for grain yields.Our study analysed the direction,magnitude and hierarchy of plastic responses of yieldrelated traits(i.e.biomass allocation and yield components)of rice(Oryza sativa L.)to nutrient availability.We estimated the effect of inoculation with arbuscular mycorrhizal fungi(AMF)on these characteristics of phenotypic plasticity.Methods A field experiment was carried out in northeast China,providing rice with six NPK fertilizer levels with or without inoculation with Glomus mosseae.At maturity,we quantified biomass allocation traits(shoot:root ratio and panicle:shoot ratio)and yield component traits(panicle number per hill,spikelet number per panicle,percentage of filled spikelets and seed weight).We also assessed the direction of change in each trait and the magnitude of trait plasticity.Important Findings In non-inoculated plants,we found that biomass allocation and seed-number traits(i.e.panicle number per hill,spikelet number per panicle and percentage of filled spikelets)responded to fertilization in the same direction,increasing with rising fertilization.Panicle formation was the most plastic trait,while seed mass was the least plastic trait.AMF inoculation nullified the relationship between most biomass allocation and seed-number traits(except for that between panicle:shoot ratio and the percentage of filled spikelets)but increased the magnitude of plasticity in biomass allocation traits without altering the hierarchy of traits’plasticity.These results underscore the importance of plasticity of yield-related traits per se,and the impact of AMF on plasticity,for maintaining rice yields under low fertilization regimes.展开更多
The ultrasonic pulse signal resonance features in layered carbon fiber reinforced plastic（CFRP） within voids were researched. The frequency domain model of acoustic wave propagation in multilayered medium was establ...The ultrasonic pulse signal resonance features in layered carbon fiber reinforced plastic（CFRP） within voids were researched. The frequency domain model of acoustic wave propagation in multilayered medium was established. Then the reflection coefficient of multilayered CFRP within voids was numerically calculated. The results are as follows. When the CFRP laminate is tested by ultrasonic whose center frequency is close to the CFRP inherent resonant frequency, the ultrasonic may generate resonance phenomenon in CFRP. If CFRP contains evenly distributed voids, the frequency of resonant signal and its amplitude all decrease with the increase of porosity. For the thick section CFRP within local concentrated voids, the local concentrated voids near testing surface will cause signal frequency reduction and the decrease of its amplitude. But the voids which exist in layers far away from testing surface almost have no influence on signal resonance. The ultrasonic pulse echo testing was conducted for thick section CFRP specimen. The analysis results of testing signals were in accordance with the results of the numerical calculation, showing that the reflection coefficient frequency response model can effectively explain the ultrasonic resonance phenomenon in layered CFRP within voids.展开更多
Xanthium italicum is a globally distributed invasive weed that causes significant ecological and agricultural damage in the invaded areas.Although multiple mechanisms have been reported to contribute to its invasive s...Xanthium italicum is a globally distributed invasive weed that causes significant ecological and agricultural damage in the invaded areas.Although multiple mechanisms have been reported to contribute to its invasive success,the extent to which intraspecific differentiation and phenotypic plasticity facilitate this process in invaded habitats remains insufficiently understood.In this study,we conducted a common garden experiment with three nitrogen treatments: no nitrogen addition (NN),low nitrogen (LN: 2 g urea per pot),and high nitrogen (HN: 4 g urea per pot).Ten populations of invasive X.italicum (ten individuals per population,100 individuals total) and native Xanthium sibiricum (excluded from the NN treatment due to seed limitations) were grown under each nitrogen treatments.Under the NN treatment,we detected significant phenotypic differences among different invasive X.italicum populations across six growth traits (root length,shoot length,crown breadth,base diameter,relative chlorophyll content,and biomass).Furthermore,when subjected to the LN and HN treatments,invasive X.italicum exhibited significantly higher phenotypic plasticity compared with that of native X.sibiricum in biomass and base diameter.Our findings suggest that phenotypic plasticity and intraspecific differentiation may play important roles in facilitating the invasive success of X.italicum in China,potentially increasing the risk of further biological invasion.展开更多
Background Biological invasions pose severe threats to global biodiversity and human well-being.Invading populations often experience negative growth rates during the‘lag phase',leading to Allee effects,a density...Background Biological invasions pose severe threats to global biodiversity and human well-being.Invading populations often experience negative growth rates during the‘lag phase',leading to Allee effects,a density-dependent phenomenon.Allee effects reduce species fitness or plant performance due to low-density populations.The rapid spread and range expansion of an invader,Hyptis suaveolens(L.)Poit.has been reported to have negative impacts on local biodiversity in the invaded regions of the Vindhyan highlands,India.The present study examines the effects of varied population densities of H.suaveolens on its vegetative trait performance,reproductive output,and density-dependent plant population regulations.Understanding the relationship between the population density and trait modulation ability of H.suaveolens at fine and coarse scales could help strategize for management.Methods The study was conducted in invaded habitats of H.suaveolens in the Vindhyan highlands,India.Population density was divided into low-,medium-,and high-density groups.Plant performance was assessed at two scales—fine scale and coarse scale.Plant performance traits,vegetative growth,and reproductive output were estimated as plant traits(Pl Ts)at the fine scale and patch traits(Pa Ts)at the coarse scale.The plasticity response index(PI)was also estimated among three population densities.Results Results showed that Pl Ts-vegetative and reproductive traits,such as plant height,biomass,and number of seeds,were significantly different across densities,with medium-density individuals showing maximum plant height and plant biomass and high-density individuals exhibiting a higher number of seeds per plant.Pa Ts analysis revealed that plant biomass per patch was similar for medium-and high-density populations,whereas the number of seeds per patch was similar in low-and medium-density populations.PI values revealed that Pl Ts showed low,medium,and high plastic responses,while Pa Ts exhibited low and high plastic responses.Conclusions The study concludes that H.suaveolens exhibits density-dependent plant population regulations.As population density increases,low-density populations grow more rapidly,resulting in denser populations.These populations can negatively impact recipient habitats and,if left unchecked,grow into high-density populations with higher seed production.The study suggests that low-density areas should be considered a high priority for developing efficient and cost-effective management strategies.The present study emphasizes the importance of incorporating Allee effects dynamics in invasion studies for predicting high-risk/priority areas for strategizing invasive species management.展开更多
基金The project supported by a fund from the National Educational Committee.
文摘Based on energy equilibrium,a new procedure called the Membrane Factor Method is devel- oped to analyze the dynamic plastic response of plates with deflections in the range where both bending mo- ments and membrane forces are important.The final deflection of a simply -supported circular rigid-plastic plate loaded by a uniformly distributed impulse is obtained.In comparison with other approximate solutions, the present results are found to be simpler and in better agreement with the corresponding experimental values reoorded by Florence.
文摘Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is complicated by their discontinuity and inhomogeneity. The finite element method (FEM) and the finite strip method are usually adopted in their analysis. Although many useful conclusions have been obtained, the computational cost is enormous. Based on some assumptions, the dynamic plastic response of clamped stiffened plates with large deflections was theoretically investigated herein by a singly symmetric beam model. Firstly, the deflection conditions that a plastic string must satisfy were obtained by the linearized moment-axial force interaction curve for singly symmetric cross sections and the associated plastic flow rule. Secondly, the possible motion mechanisms of the beam under different load intensity were analysed in detail. For structures with plastic deformations, a simplified method was then given that the arbitrary impact load can be replaced equivalently by a rectangular pulse. Finally, to confirm the validity of the proposed method, the dynamic plastic response of a one-way stiffened plate with four fully clamped edges was calculated. The theoretical results were in good agreement with those of FEM. It indicates that the present calculation model is easy and feasible, and the equivalent substitution of load almost has no influence on the final deflection.
文摘This paper concerns the dynamic plastic response of a circular plate resting on fluid subjected to a uniformly distributed rectangular load pulse with finite deformation. It is assumed that the fluid is incompressible and inviscous, and the plate is made of rigid-plastic material and simply supported along its edge. By using the method of the Hankel integral transformation, the nonuniform fluid resistance is derived as the plate and the fluid is coupled. Finally, an analytic solution for a circular plate under a medium load is obtained according to the equations of motion of the plate with finite deformation.
文摘The large deflection dynamic plastic response of fully clamped square plates with stiffeners under blast load is analyzed in detail in this paper. Various relevant motion patterns and criterions are presented. The formulas of maximum permanent deformation of the plates with stiffeners are derived. The results of calculation are compared with those of experiment in [3], with good agreement shown in most cases.
文摘In this paper the problem of a circular beam subjected to radial impact by a rigid mass at its lip in its own plane is investigaleil on the basis of rigid-perfectly plastic assumption. The analytical solution of the particle velocities is obtained as the junction of travelling plastic hinge location. Ky analysing the solution, some special properties oj circular beam problem are found.
基金Project supported by the National Natural Science Foundation of China (No.10272011).
文摘The rigid, perfectly plastic dynamic response of a free-free beam subjected to impact by a projectile at any cross-section is studied. The instantaneous deformations of the beam are given through an analysis of the complete solution for rigid plastic structures. The in?uence of some parameters such as the input energy and mass ratio on the plastic deformation, travelling plastic hinge position and energy partitioning of the beam are discussed.
文摘Aim To analyze dynamic failure of aerospace strutures subjected lateral impulsive loading. Methods Structures were modeled as rigid-perfectly plastic free-free stepped beams. Basic equations of motion un set up for analysis. Results Final pat deformation and rigid motion solutions were determined for a uniform impulsive loading. The critical rupture conditions for a space shuttle and a missile were obtained. Conclusion Failure is possible for aerospace structures under a uniform impulsive loading, but it is mere difficult in space.
文摘A theoretical analysis is presented for the dynamic plastic behavior of a simply supported rigid, perfectly plastic circular plate in damping medium with finite-deflections subjected to a rectangular pressure pulse. Analytical solutions of every moving stage under both medium and high loads are developed.
基金National Natural Science Foundation of China(51179041)Major Science and Technology Program for Water Pollution Control and Treatment(2012ZX07201003)+3 种基金Natural Science Foundation of Hei Longjiang Province,China(E201206)State Key Lab of Urban Water Resource and Environment(Harbin Institute of Technology)(2014TS05)ARC Centre of Excellence in Plant Energy Biology(CE140100008 to O.K.A.)ARC Linkage grant(LP0990330 to O.K.A.).
文摘Aims Changes in the phenotype of crops(phenotypic plasticity)are known to play an important role in determining responses to nutrient availability,with the direction and magnitude of plasticity of individual traits being crucial for grain yields.Our study analysed the direction,magnitude and hierarchy of plastic responses of yieldrelated traits(i.e.biomass allocation and yield components)of rice(Oryza sativa L.)to nutrient availability.We estimated the effect of inoculation with arbuscular mycorrhizal fungi(AMF)on these characteristics of phenotypic plasticity.Methods A field experiment was carried out in northeast China,providing rice with six NPK fertilizer levels with or without inoculation with Glomus mosseae.At maturity,we quantified biomass allocation traits(shoot:root ratio and panicle:shoot ratio)and yield component traits(panicle number per hill,spikelet number per panicle,percentage of filled spikelets and seed weight).We also assessed the direction of change in each trait and the magnitude of trait plasticity.Important Findings In non-inoculated plants,we found that biomass allocation and seed-number traits(i.e.panicle number per hill,spikelet number per panicle and percentage of filled spikelets)responded to fertilization in the same direction,increasing with rising fertilization.Panicle formation was the most plastic trait,while seed mass was the least plastic trait.AMF inoculation nullified the relationship between most biomass allocation and seed-number traits(except for that between panicle:shoot ratio and the percentage of filled spikelets)but increased the magnitude of plasticity in biomass allocation traits without altering the hierarchy of traits’plasticity.These results underscore the importance of plasticity of yield-related traits per se,and the impact of AMF on plasticity,for maintaining rice yields under low fertilization regimes.
基金Funded by the National Natural Science Foundation of China(Nos.5161101582 and 51575541)Zhejiang Provincial Natural Science Foundation of China(No.LY15E050012)Zhejiang Provincial Public Projects on Industrial Technology(No.2015C31052)
文摘The ultrasonic pulse signal resonance features in layered carbon fiber reinforced plastic（CFRP） within voids were researched. The frequency domain model of acoustic wave propagation in multilayered medium was established. Then the reflection coefficient of multilayered CFRP within voids was numerically calculated. The results are as follows. When the CFRP laminate is tested by ultrasonic whose center frequency is close to the CFRP inherent resonant frequency, the ultrasonic may generate resonance phenomenon in CFRP. If CFRP contains evenly distributed voids, the frequency of resonant signal and its amplitude all decrease with the increase of porosity. For the thick section CFRP within local concentrated voids, the local concentrated voids near testing surface will cause signal frequency reduction and the decrease of its amplitude. But the voids which exist in layers far away from testing surface almost have no influence on signal resonance. The ultrasonic pulse echo testing was conducted for thick section CFRP specimen. The analysis results of testing signals were in accordance with the results of the numerical calculation, showing that the reflection coefficient frequency response model can effectively explain the ultrasonic resonance phenomenon in layered CFRP within voids.
基金supported by the Central Publicinterest Scientific Institution Basal Research Fund (No. 1610012024003)。
文摘Xanthium italicum is a globally distributed invasive weed that causes significant ecological and agricultural damage in the invaded areas.Although multiple mechanisms have been reported to contribute to its invasive success,the extent to which intraspecific differentiation and phenotypic plasticity facilitate this process in invaded habitats remains insufficiently understood.In this study,we conducted a common garden experiment with three nitrogen treatments: no nitrogen addition (NN),low nitrogen (LN: 2 g urea per pot),and high nitrogen (HN: 4 g urea per pot).Ten populations of invasive X.italicum (ten individuals per population,100 individuals total) and native Xanthium sibiricum (excluded from the NN treatment due to seed limitations) were grown under each nitrogen treatments.Under the NN treatment,we detected significant phenotypic differences among different invasive X.italicum populations across six growth traits (root length,shoot length,crown breadth,base diameter,relative chlorophyll content,and biomass).Furthermore,when subjected to the LN and HN treatments,invasive X.italicum exhibited significantly higher phenotypic plasticity compared with that of native X.sibiricum in biomass and base diameter.Our findings suggest that phenotypic plasticity and intraspecific differentiation may play important roles in facilitating the invasive success of X.italicum in China,potentially increasing the risk of further biological invasion.
基金the Institution of Eminence(IOE),University of Delhithe Science and Engineering Research Board,Department of Science and Technology,India
文摘Background Biological invasions pose severe threats to global biodiversity and human well-being.Invading populations often experience negative growth rates during the‘lag phase',leading to Allee effects,a density-dependent phenomenon.Allee effects reduce species fitness or plant performance due to low-density populations.The rapid spread and range expansion of an invader,Hyptis suaveolens(L.)Poit.has been reported to have negative impacts on local biodiversity in the invaded regions of the Vindhyan highlands,India.The present study examines the effects of varied population densities of H.suaveolens on its vegetative trait performance,reproductive output,and density-dependent plant population regulations.Understanding the relationship between the population density and trait modulation ability of H.suaveolens at fine and coarse scales could help strategize for management.Methods The study was conducted in invaded habitats of H.suaveolens in the Vindhyan highlands,India.Population density was divided into low-,medium-,and high-density groups.Plant performance was assessed at two scales—fine scale and coarse scale.Plant performance traits,vegetative growth,and reproductive output were estimated as plant traits(Pl Ts)at the fine scale and patch traits(Pa Ts)at the coarse scale.The plasticity response index(PI)was also estimated among three population densities.Results Results showed that Pl Ts-vegetative and reproductive traits,such as plant height,biomass,and number of seeds,were significantly different across densities,with medium-density individuals showing maximum plant height and plant biomass and high-density individuals exhibiting a higher number of seeds per plant.Pa Ts analysis revealed that plant biomass per patch was similar for medium-and high-density populations,whereas the number of seeds per patch was similar in low-and medium-density populations.PI values revealed that Pl Ts showed low,medium,and high plastic responses,while Pa Ts exhibited low and high plastic responses.Conclusions The study concludes that H.suaveolens exhibits density-dependent plant population regulations.As population density increases,low-density populations grow more rapidly,resulting in denser populations.These populations can negatively impact recipient habitats and,if left unchecked,grow into high-density populations with higher seed production.The study suggests that low-density areas should be considered a high priority for developing efficient and cost-effective management strategies.The present study emphasizes the importance of incorporating Allee effects dynamics in invasion studies for predicting high-risk/priority areas for strategizing invasive species management.
