The microstructural evolution and precipitation behaviour of Nb–V–Mo and single V containing transformation induced plasticity assisted steels were investigated during thermomechanical processing. A plane strain com...The microstructural evolution and precipitation behaviour of Nb–V–Mo and single V containing transformation induced plasticity assisted steels were investigated during thermomechanical processing. A plane strain compression testing machine was used to simulate the thermomechanical processing. Microstructures were characterised by optical microscopy, scanning-transmission electron microscopy and microanalysis, and X-ray diffraction analysis, and Vickers hardness was obtained from the deformed specimens. The resulting microstructure of both Nb–V–Mo and V steels at room temperature primarily consisted of an acicular/bainitic ferrite, retained austenite and martensite surrounded by allotriomorphic ferrite.The TEM analysis showed that a significant number of Nb（V,Mo）（C,N） precipitates were formed in the microstructure down to the finishing stage in Nb–V–Mo steel（i.e. 830℃）. It was also found that the V（C,N）precipitation primarily occurred in both ferrite and deformed austenite below the finishing stage. The results suggested that Nb–Mo additions considerably increased the temperature stability of microalloy precipitates and controlled the microstructural evolution of austenite. However, the microalloy precipitation did not cause a significant precipitation strengthening in both Nb–V–Mo and V steels at room temperature.展开更多
Three different Cu-Zr-Co alloys, namely Cu40Zr37.5Co22.5, Cu42.5Zr45Co12.5 and Cu49Zr49Co2, were obtained by rapid cooling. The microstructure and phase formation of as-cast rods with diameters of 2 mm are compared wi...Three different Cu-Zr-Co alloys, namely Cu40Zr37.5Co22.5, Cu42.5Zr45Co12.5 and Cu49Zr49Co2, were obtained by rapid cooling. The microstructure and phase formation of as-cast rods with diameters of 2 mm are compared with those of the respective ingots. An increasing Co content stabilises the B2 CuZr phase and leads to the precipitation of a ternary Cu-Zr-Co phase. The variation of the cooling rate affects the size of the B2 dendrites as well as the volume fraction and the morphology of the interdendritic phases. The mechanical properties were determined in compression and all alloys show a certain plastic deformability despite the presence of several binary and ternary intermetallic phases. The deformation mechanisms are discussed on the basis of the microstructures and the constituent phases.展开更多
Compared to intact coal,tectonic coal exhibits unique characteristics.The deformation behaviours under cyclic loading with different confining pressures and loading rates are monitored by MTS815 test system,and the me...Compared to intact coal,tectonic coal exhibits unique characteristics.The deformation behaviours under cyclic loading with different confining pressures and loading rates are monitored by MTS815 test system,and the mechanical and energy properties are analysed using experimental data.The results show that the stress-strain curve could be divided into four stages in a single cycle.The elastic strain and elastic energy density increase linearly with deviatoric stress and are proportional to the confining pressure and loading rate;irreversible strain and dissipated energy density increase exponentially with deviatoric stress,inversely proportional to the confining pressure and loading rate.The internal structure of tectonic coal is divided into three types,all of which are damaged under different deviatoric stress levels,thereby explaining the segmentation phenomenon of stress-strain curve of tectonic coal in the cyclic loading process.Tectonic coal exhibits nonlinear energy storage characteristics,which verifies why the tectonic coal is prone to coal and gas outburst from the principle of energy dissipation.In addition,the damage mechanism of tectonic coal is described from the point of energy distribution by introducing the concepts of crushing energy and friction energy.展开更多
We studied the locomotor behaviour of white-headed langurs Trachypithecus leucocephalus and Francois＇ langurs T.francoisi to test two hypotheses： （1） these monkeys have evolved locomotor ability to support their a...We studied the locomotor behaviour of white-headed langurs Trachypithecus leucocephalus and Francois＇ langurs T.francoisi to test two hypotheses： （1） these monkeys have evolved locomotor ability to support their activities on limestone hills, and （2） Francois＇ langurs have evolved more diverse locomotor skills than white-headed langurs. Data were collected from 1996 - 1998 and in 2005 in Fusui Nature Reserve, Guangxi, and showed that the two species had similar locomotor types, but Francois＇ langurs had more locomotor modes （26） than white-headed langurs （12）. Quadrupedal walking and leaping were two major types, and white-headed langurs were more arboreal than Francois＇ langurs. We suggest that, while keeping their ancestral locomotor types, the two species have evolved new types allowing them to live on limestone cliffs. Compared to white-headed langurs, Francois＇ langurs have more diverse locomotor modes that probably have allowed them to live in more habitat types. As an evolutionary outcome, Francois＇ langurs have a larger distribution range .展开更多
Canus lupus familiais (domestic dogs) tend to elicit from (the sign stimulus of) a friendly greeting, improved effectiveness of behaviour, an (observable) innate, likely hormonal, (possibly oxytocin) mediated response...Canus lupus familiais (domestic dogs) tend to elicit from (the sign stimulus of) a friendly greeting, improved effectiveness of behaviour, an (observable) innate, likely hormonal, (possibly oxytocin) mediated response (a Mebir). Breakthroughs in the natural and behavioural sciences, political ideology, and education come from evidence for {1} the Mebir, {2} the theorem, humans are loving, non-competitive, and non-aggressive (in part from two new theories of evolution), and {3} the Mebir providing social species with cultural and evolutionary freedom (e.g. the social brain hypothesis is substantiated). Other social species (including humans and songbirds), and possibly “non-social” species (e.g., including domestic cats) likely undergo a Mebir. Social species more frequently undergo social interactions suggesting they more frequently undergo the Mebir, and therefore have greater cultural and evolutionary freedom. Two hypotheses were tested and proven invalid. Friendly greetings do not make dogs more effective in behaviour (nor do they invoke innate hunting behaviours as a displaced innate response (that in wolves improve fitness)) (N = 50), and do not make dogs walk faster (N = 29). Data are inclusive of various dog breeds, mixed breeds, both sexes, and all ages from chance encounters with dogs being walked on a sidewalk in a naturalistic setting. Three synchronous greetings were used to elicit the Mebir in dogs, eye contact, friendly verbal greetings, and handwaves. Behavioural responses were commonly exaggerated but weak for certain individuals. Responses included heightened curiosity (about objects and the environment), courageous exploration, creative and playful behaviour, assertiveness (e.g., in pulling on the leash), “pronounced social affiliation seeking” with dogs, pedestrians, and the dog’s owner, heightened aggressiveness (when territorial), and perhaps heightened concentration. Past research indicates that dog learning is improved from social interactions with humans.展开更多
This paper deals with a non-local parabolic equation of Lotka-Volterra type that describes the evolution of phenotypically structured populations. Nonlinearities appear in these systems to model interactions and compe...This paper deals with a non-local parabolic equation of Lotka-Volterra type that describes the evolution of phenotypically structured populations. Nonlinearities appear in these systems to model interactions and competition phenomena leading to selection. In this paper, the equation on the structured population is coupled with a differential equation on the nutrient concentration that changes as the total population varies.Different methods aimed at showing the convergence of the solutions to a moving Dirac mass are reviewed. Using either weak or strong regularity assumptions, the authors study the concentration of the solution. To this end, BV estimates in time on appropriate quantities are stated, and a constrained Hamilton-Jacobi equation to identify where the solutions concentrates as Dirac masses is derived.展开更多
The effect of hydrogen addition on compression deformation behaviour of Ti-0.3Mo-0.8Ni alloy argon-arc welded joint has been investigated.Evolution mechanism of hydrogen-induced flow stress was discussed in detail.The...The effect of hydrogen addition on compression deformation behaviour of Ti-0.3Mo-0.8Ni alloy argon-arc welded joint has been investigated.Evolution mechanism of hydrogen-induced flow stress was discussed in detail.The results show that with increasing hydrogen content,the stretching and bending extent of fully lamellar microstructures including ot lamellas and acicular hydride continued to increase,the morphology of dynamic recrystallization(DRX)grains tended to change from approximately equiaxed to large lamellar shape,and the quantity of DRX grains and recrystallization degree of grains increased obviously.A large number of dislocations concentrated in the vicinity of the hydride.Steady stress was decreased continuously with increasing hydrogen content,while peak stress of the hydrogenated 0.12 wt.% H weld zone was decreased to the minimum value and then increased slowly.A slight decrease in flow stress of the hydrogenated 0.05 wt.% H weld zone was caused by limited increase in the volume fraction of softer βphase.Hydrogen-induced DRX of a phase and improved dislocation movement by strong interaction between the hydride and dislocation directly resulted in a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone.Solute hydrogen also finitely contributed to a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone by promoted local softening,which induced continuous DRX and more movable dislocations to participate in slipping or climbing.The reinforcement effect and plastic deformation of the hydride and solution strengthening of P phase induced by solute hydrogen finally led to the increase in flow stress of the hydrogenated 0.21 wt.% H weld zone in its true strain range from 0 to 0.36.展开更多
Bentonite-based materials have been considered in many countries as engineered barrier/backfilling materials in deep geological disposal of high-level radioactive waste.During the long period of waste storage,these ma...Bentonite-based materials have been considered in many countries as engineered barrier/backfilling materials in deep geological disposal of high-level radioactive waste.During the long period of waste storage,these materials will play an essential role in ensuring the integrity of the storage system that consists of the waste canisters,the engineered barrier/backfill,the retaining structures as well as the geological barrier.Thus,it is essential to well understand the hydro-mechanical behaviours of these bentonite-based materials.This review paper presents the recent advances of knowledge on MX80 bentonite-based materials,in terms of water retention properties,hydraulic behaviour and mechanical behaviour.Emphasis is put on the effect of technological voids and the role of the dry density of bentonite.The swelling anisotropy is also discussed based on the results from swelling tests with measurements of both axial and radial swelling pressures on a sand-bentonite mixture compacted at different densities.Microstructure observation was used to help the interpretation of macroscopic hydromechanical behaviour.Also,the evolution of soil microstructure thus the soil density over time is discussed based on the results from mock-up tests.This evolution is essential for understanding the longterm hydro-mechanical behaviour of the engineered barrier/backfill.展开更多
This paper proposes a pest propagation model to investigate the evolution behaviours of pest aggregates. A pest aggregate grows by self-monomer birth, and it may fragment into two smaller ones. The kinetic evolution b...This paper proposes a pest propagation model to investigate the evolution behaviours of pest aggregates. A pest aggregate grows by self-monomer birth, and it may fragment into two smaller ones. The kinetic evolution behaviours of pest aggregates are investigated by the rate equation approach based on the mean-field theory. For a system with a self-birth rate kernel I（k） = Ik and a fragmentation rate kernel L（i,j） = L, we find that the total number MoA（t） and the total mass of the pest aggregates MA （t） both increase exponentially with time if L ≠ 0. Furthermore, we introduce two catalysis-driven monomer death mechanisms for the former pest propagation model to study the evolution behaviours of pest aggregates under pesticide and natural enemy controlled pest propagation. In the pesticide controlled model with a catalyzed monomer death rate kernel J1 （k） ---- J1 k, it is found that only when I 〈 J1 B0 （B0 is the concentration of catalyst aggregates） can the pests be killed off. Otherwise, the pest aggregates can survive. In the model of pest control with a natural enemy, a pest aggregate loses one of its individuals and the number of natural enemies increases by one. For this system, we find that no matter how many natural enemies there are at the beginning, pests will be eliminated by them eventually.展开更多
In the paper the evolution equations are discussed so as to enable aphenomenological description of microstruchtral behaviour e.g . partially reversible flowof Maxwellian gas, recovery structural relaxation and other ...In the paper the evolution equations are discussed so as to enable aphenomenological description of microstruchtral behaviour e.g . partially reversible flowof Maxwellian gas, recovery structural relaxation and other experimental results coming from light scattering and molecular dynamics .The result deals with the revaluation of Zaremba s ansatz.It leads to resolution of problems with substantial and available nonlinearities in the transport equation.展开更多
文摘The microstructural evolution and precipitation behaviour of Nb–V–Mo and single V containing transformation induced plasticity assisted steels were investigated during thermomechanical processing. A plane strain compression testing machine was used to simulate the thermomechanical processing. Microstructures were characterised by optical microscopy, scanning-transmission electron microscopy and microanalysis, and X-ray diffraction analysis, and Vickers hardness was obtained from the deformed specimens. The resulting microstructure of both Nb–V–Mo and V steels at room temperature primarily consisted of an acicular/bainitic ferrite, retained austenite and martensite surrounded by allotriomorphic ferrite.The TEM analysis showed that a significant number of Nb（V,Mo）（C,N） precipitates were formed in the microstructure down to the finishing stage in Nb–V–Mo steel（i.e. 830℃）. It was also found that the V（C,N）precipitation primarily occurred in both ferrite and deformed austenite below the finishing stage. The results suggested that Nb–Mo additions considerably increased the temperature stability of microalloy precipitates and controlled the microstructural evolution of austenite. However, the microalloy precipitation did not cause a significant precipitation strengthening in both Nb–V–Mo and V steels at room temperature.
基金the financial support by CNPq, Brazil, and DAAD, Germany
文摘Three different Cu-Zr-Co alloys, namely Cu40Zr37.5Co22.5, Cu42.5Zr45Co12.5 and Cu49Zr49Co2, were obtained by rapid cooling. The microstructure and phase formation of as-cast rods with diameters of 2 mm are compared with those of the respective ingots. An increasing Co content stabilises the B2 CuZr phase and leads to the precipitation of a ternary Cu-Zr-Co phase. The variation of the cooling rate affects the size of the B2 dendrites as well as the volume fraction and the morphology of the interdendritic phases. The mechanical properties were determined in compression and all alloys show a certain plastic deformability despite the presence of several binary and ternary intermetallic phases. The deformation mechanisms are discussed on the basis of the microstructures and the constituent phases.
基金funded by the National Major Scientific Research Instrument Development Project(No.41727801)the National Natural Science Foundation of China(Nos.42030810 and 41972168)+1 种基金the Dominant discipline support project of Jiangsu Province(No.2020CXNL11)the Foundation of Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization(No.2019A001).
文摘Compared to intact coal,tectonic coal exhibits unique characteristics.The deformation behaviours under cyclic loading with different confining pressures and loading rates are monitored by MTS815 test system,and the mechanical and energy properties are analysed using experimental data.The results show that the stress-strain curve could be divided into four stages in a single cycle.The elastic strain and elastic energy density increase linearly with deviatoric stress and are proportional to the confining pressure and loading rate;irreversible strain and dissipated energy density increase exponentially with deviatoric stress,inversely proportional to the confining pressure and loading rate.The internal structure of tectonic coal is divided into three types,all of which are damaged under different deviatoric stress levels,thereby explaining the segmentation phenomenon of stress-strain curve of tectonic coal in the cyclic loading process.Tectonic coal exhibits nonlinear energy storage characteristics,which verifies why the tectonic coal is prone to coal and gas outburst from the principle of energy dissipation.In addition,the damage mechanism of tectonic coal is described from the point of energy distribution by introducing the concepts of crushing energy and friction energy.
文摘We studied the locomotor behaviour of white-headed langurs Trachypithecus leucocephalus and Francois＇ langurs T.francoisi to test two hypotheses： （1） these monkeys have evolved locomotor ability to support their activities on limestone hills, and （2） Francois＇ langurs have evolved more diverse locomotor skills than white-headed langurs. Data were collected from 1996 - 1998 and in 2005 in Fusui Nature Reserve, Guangxi, and showed that the two species had similar locomotor types, but Francois＇ langurs had more locomotor modes （26） than white-headed langurs （12）. Quadrupedal walking and leaping were two major types, and white-headed langurs were more arboreal than Francois＇ langurs. We suggest that, while keeping their ancestral locomotor types, the two species have evolved new types allowing them to live on limestone cliffs. Compared to white-headed langurs, Francois＇ langurs have more diverse locomotor modes that probably have allowed them to live in more habitat types. As an evolutionary outcome, Francois＇ langurs have a larger distribution range .
文摘Canus lupus familiais (domestic dogs) tend to elicit from (the sign stimulus of) a friendly greeting, improved effectiveness of behaviour, an (observable) innate, likely hormonal, (possibly oxytocin) mediated response (a Mebir). Breakthroughs in the natural and behavioural sciences, political ideology, and education come from evidence for {1} the Mebir, {2} the theorem, humans are loving, non-competitive, and non-aggressive (in part from two new theories of evolution), and {3} the Mebir providing social species with cultural and evolutionary freedom (e.g. the social brain hypothesis is substantiated). Other social species (including humans and songbirds), and possibly “non-social” species (e.g., including domestic cats) likely undergo a Mebir. Social species more frequently undergo social interactions suggesting they more frequently undergo the Mebir, and therefore have greater cultural and evolutionary freedom. Two hypotheses were tested and proven invalid. Friendly greetings do not make dogs more effective in behaviour (nor do they invoke innate hunting behaviours as a displaced innate response (that in wolves improve fitness)) (N = 50), and do not make dogs walk faster (N = 29). Data are inclusive of various dog breeds, mixed breeds, both sexes, and all ages from chance encounters with dogs being walked on a sidewalk in a naturalistic setting. Three synchronous greetings were used to elicit the Mebir in dogs, eye contact, friendly verbal greetings, and handwaves. Behavioural responses were commonly exaggerated but weak for certain individuals. Responses included heightened curiosity (about objects and the environment), courageous exploration, creative and playful behaviour, assertiveness (e.g., in pulling on the leash), “pronounced social affiliation seeking” with dogs, pedestrians, and the dog’s owner, heightened aggressiveness (when territorial), and perhaps heightened concentration. Past research indicates that dog learning is improved from social interactions with humans.
基金supported by ANR-13-BS01-0004 funded by the French Ministry of Research(ANR Kibord)
文摘This paper deals with a non-local parabolic equation of Lotka-Volterra type that describes the evolution of phenotypically structured populations. Nonlinearities appear in these systems to model interactions and competition phenomena leading to selection. In this paper, the equation on the structured population is coupled with a differential equation on the nutrient concentration that changes as the total population varies.Different methods aimed at showing the convergence of the solutions to a moving Dirac mass are reviewed. Using either weak or strong regularity assumptions, the authors study the concentration of the solution. To this end, BV estimates in time on appropriate quantities are stated, and a constrained Hamilton-Jacobi equation to identify where the solutions concentrates as Dirac masses is derived.
基金The authors would like to gratefully acknowledge that this work was supported by the China Postdoctoral Science Foundation(Grant No.2020M672306)National Natural Science Foundation of China(Grant Nos.51874225 and 51671152).
文摘The effect of hydrogen addition on compression deformation behaviour of Ti-0.3Mo-0.8Ni alloy argon-arc welded joint has been investigated.Evolution mechanism of hydrogen-induced flow stress was discussed in detail.The results show that with increasing hydrogen content,the stretching and bending extent of fully lamellar microstructures including ot lamellas and acicular hydride continued to increase,the morphology of dynamic recrystallization(DRX)grains tended to change from approximately equiaxed to large lamellar shape,and the quantity of DRX grains and recrystallization degree of grains increased obviously.A large number of dislocations concentrated in the vicinity of the hydride.Steady stress was decreased continuously with increasing hydrogen content,while peak stress of the hydrogenated 0.12 wt.% H weld zone was decreased to the minimum value and then increased slowly.A slight decrease in flow stress of the hydrogenated 0.05 wt.% H weld zone was caused by limited increase in the volume fraction of softer βphase.Hydrogen-induced DRX of a phase and improved dislocation movement by strong interaction between the hydride and dislocation directly resulted in a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone.Solute hydrogen also finitely contributed to a sharp drop in flow stress of the hydrogenated 0.12 and 0.21 wt.% H weld zone by promoted local softening,which induced continuous DRX and more movable dislocations to participate in slipping or climbing.The reinforcement effect and plastic deformation of the hydride and solution strengthening of P phase induced by solute hydrogen finally led to the increase in flow stress of the hydrogenated 0.21 wt.% H weld zone in its true strain range from 0 to 0.36.
文摘Bentonite-based materials have been considered in many countries as engineered barrier/backfilling materials in deep geological disposal of high-level radioactive waste.During the long period of waste storage,these materials will play an essential role in ensuring the integrity of the storage system that consists of the waste canisters,the engineered barrier/backfill,the retaining structures as well as the geological barrier.Thus,it is essential to well understand the hydro-mechanical behaviours of these bentonite-based materials.This review paper presents the recent advances of knowledge on MX80 bentonite-based materials,in terms of water retention properties,hydraulic behaviour and mechanical behaviour.Emphasis is put on the effect of technological voids and the role of the dry density of bentonite.The swelling anisotropy is also discussed based on the results from swelling tests with measurements of both axial and radial swelling pressures on a sand-bentonite mixture compacted at different densities.Microstructure observation was used to help the interpretation of macroscopic hydromechanical behaviour.Also,the evolution of soil microstructure thus the soil density over time is discussed based on the results from mock-up tests.This evolution is essential for understanding the longterm hydro-mechanical behaviour of the engineered barrier/backfill.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10875086 and 10775104)
文摘This paper proposes a pest propagation model to investigate the evolution behaviours of pest aggregates. A pest aggregate grows by self-monomer birth, and it may fragment into two smaller ones. The kinetic evolution behaviours of pest aggregates are investigated by the rate equation approach based on the mean-field theory. For a system with a self-birth rate kernel I（k） = Ik and a fragmentation rate kernel L（i,j） = L, we find that the total number MoA（t） and the total mass of the pest aggregates MA （t） both increase exponentially with time if L ≠ 0. Furthermore, we introduce two catalysis-driven monomer death mechanisms for the former pest propagation model to study the evolution behaviours of pest aggregates under pesticide and natural enemy controlled pest propagation. In the pesticide controlled model with a catalyzed monomer death rate kernel J1 （k） ---- J1 k, it is found that only when I 〈 J1 B0 （B0 is the concentration of catalyst aggregates） can the pests be killed off. Otherwise, the pest aggregates can survive. In the model of pest control with a natural enemy, a pest aggregate loses one of its individuals and the number of natural enemies increases by one. For this system, we find that no matter how many natural enemies there are at the beginning, pests will be eliminated by them eventually.
文摘In the paper the evolution equations are discussed so as to enable aphenomenological description of microstruchtral behaviour e.g . partially reversible flowof Maxwellian gas, recovery structural relaxation and other experimental results coming from light scattering and molecular dynamics .The result deals with the revaluation of Zaremba s ansatz.It leads to resolution of problems with substantial and available nonlinearities in the transport equation.
