In this work, porous Ti6Al4V alloys with 30%-70% porosity for biomedical applications were fabricated by diffusion bonding of alloy meshes. Pore structure was characterized by Micro-CT and SEM. Compressive behavior in...In this work, porous Ti6Al4V alloys with 30%-70% porosity for biomedical applications were fabricated by diffusion bonding of alloy meshes. Pore structure was characterized by Micro-CT and SEM. Compressive behavior in the out-of-plane direction and biocompatibility with cortical bone were studied. The results reveal that the fabricated porous Ti6Al4V alloys possess anisotropic structure with square pores in the in-plane direction and elongated pores in the out-of-plane direction. The average pore size of porous Ti6Al4V alloys with 30%-70% porosity is in the range of 240-360 Bin. By tailoring diffusion bonding temperature, aspect ratio of alloy meshes and porosity, porous Ti6Al4V alloys with different compressive properties can be obtained, for instance, Young＇s modulus and yield stress in the ranges of 4-40 GPa and 70-500 MPa, respectively. Yield stress of porous Ti6Al4V alloys fabricated by diffusion bonding is close to that of alloys fabricated by rapid prototyping, hut higher than that of fabricated by powder sintering and space-holder method. Diffusion bonding temperature has some effects on the yield stress of porous Ti6Al4V alloys, but has a minor effect on the Young＇s modulus. The relationship between compressive properties and relative density conforms well to the Gibson-Ashby model. The Young＇s modulus is linear with the aspect ratio, while the yield stress is linear with the square of aspect ratio of alloy meshes. Porous Ti6Al4V alloys with 60%-70% porosity have potential for cortical bone implant applications.展开更多
The performance of gas diffusion porous electrode starved of electrolyte solution can be significantly increased by decreasing the thickness of uneven liquid film covering the catalyst agglomerates.
A coarse-grained model is proposed to study the dynamics of a nano-chain diffusing in porous media. The simulation utilizes a hybrid method which combines stochastic rotation dynamics with molecular dynamics. Solvent ...A coarse-grained model is proposed to study the dynamics of a nano-chain diffusing in porous media. The simulation utilizes a hybrid method which combines stochastic rotation dynamics with molecular dynamics. Solvent molecules are explicitly taken into account to represent the hydrodynamic interactions and random fluctuations. The conformation, relaxation, and diffusion properties of a polymer chain are investigated by changing the density degree of the obstacle matrix. It is found that the average size of the chain is a non- monotonic function of the obstacle volume faction Ф. A dense environment may contribute to extending a linear chain, which can be characterized by larger exponents in the corresponding power law. The relaxation behavior of a stretched chain to a steady state shows dramatic crossover from exponent to power-law relaxation when the values of φ are increased. The dependence of the diffusion coefficient on the chain size is also studied. Various kinds of scaling properties are presented and discussed. The results can give additional insight into the density effect of porous media on polymer structure and dynamics.展开更多
The leaching kinetics of zinc silicate in ammonium chloride solution was investigated. The effects of stirring speed （150？400 r/min）, leaching temperature （95-108 ℃, particle size of zinc silicate （61-150 μm...The leaching kinetics of zinc silicate in ammonium chloride solution was investigated. The effects of stirring speed （150？400 r/min）, leaching temperature （95-108 ℃, particle size of zinc silicate （61-150 μm） and the concentration of ammonium chloride （3.5-5.5 mol/L） on leaching rate of zinc were studied. The results show that decreasing the particle size of zinc silicate and increasing the leaching temperature and concentration of ammonium chloride can obviously enhance the leaching rate of zinc. Among the kinetic models of the porous solids tested, the grain model with porous diffusion control can well describe the zinc leaching kinetics. The apparent activation energy of the leaching reaction is 161.26 kJ/mol and the reaction order with respect to ammonium chloride is 3.5.展开更多
This paper studies the unsteady heat and mass natural convection in a highly porous medium bounded by an infinite vertical porous wall. The unsteady source of the problem arises from the transverse oscillations in suc...This paper studies the unsteady heat and mass natural convection in a highly porous medium bounded by an infinite vertical porous wall. The unsteady source of the problem arises from the transverse oscillations in suction velocity of fluids, The analytical results for the problem are obtained based on the method of small parameter, and show that the natural circulation in the porous medium is affected by this kind of oscillation.展开更多
In this paper,we deal with the following chemotaxis-haptotaxis system modeling cancer invasion with nonlinear diffusion,ut=Δum−χ∇·(u∇v)−ξ∇·(u∇ω)+μu(1−u−ω),inΩ×R^(+),vt−Δv+v=u,inΩ×R+,ωt=−v...In this paper,we deal with the following chemotaxis-haptotaxis system modeling cancer invasion with nonlinear diffusion,ut=Δum−χ∇·(u∇v)−ξ∇·(u∇ω)+μu(1−u−ω),inΩ×R^(+),vt−Δv+v=u,inΩ×R+,ωt=−vω,inΩ×R+,whereΩ⊂R^(N)is a bounded domain.We first supplement the results of global existence and uniform boundedness of solutions for the case m=2N N+2.Then for any m>0 and any spatial dimension,we consider the stability of equilibrium,and find that the chemotaxis has a destabilizing effect,that is for the ODEs,or the diffusion-ODE system without chemotaxis,the solutions tend to a linearly stable uniform steady state(1,1,0).When the chemotactic coefficientχis large,the equilibrium(1,1,0)become unstable.Then we study the existence of nontrivial stationary solutions via bifurcation techniques withχbeing the bifurcation parameter,and obtain nonhomogeneous patterns.At last,we also investigate the stability of these bifurcation solutions.展开更多
We study in this paper the first boundary value problem of one dimensional degenerate quasilinear elliptic-parabolic equation with discontinuous coefficients (layered media). The uniquenessof the weak solutions is pro...We study in this paper the first boundary value problem of one dimensional degenerate quasilinear elliptic-parabolic equation with discontinuous coefficients (layered media). The uniquenessof the weak solutions is proved under natural conditions.展开更多
基金supported by the National Basic Research Program of China (No. 2012CB619101)
文摘In this work, porous Ti6Al4V alloys with 30%-70% porosity for biomedical applications were fabricated by diffusion bonding of alloy meshes. Pore structure was characterized by Micro-CT and SEM. Compressive behavior in the out-of-plane direction and biocompatibility with cortical bone were studied. The results reveal that the fabricated porous Ti6Al4V alloys possess anisotropic structure with square pores in the in-plane direction and elongated pores in the out-of-plane direction. The average pore size of porous Ti6Al4V alloys with 30%-70% porosity is in the range of 240-360 Bin. By tailoring diffusion bonding temperature, aspect ratio of alloy meshes and porosity, porous Ti6Al4V alloys with different compressive properties can be obtained, for instance, Young＇s modulus and yield stress in the ranges of 4-40 GPa and 70-500 MPa, respectively. Yield stress of porous Ti6Al4V alloys fabricated by diffusion bonding is close to that of alloys fabricated by rapid prototyping, hut higher than that of fabricated by powder sintering and space-holder method. Diffusion bonding temperature has some effects on the yield stress of porous Ti6Al4V alloys, but has a minor effect on the Young＇s modulus. The relationship between compressive properties and relative density conforms well to the Gibson-Ashby model. The Young＇s modulus is linear with the aspect ratio, while the yield stress is linear with the square of aspect ratio of alloy meshes. Porous Ti6Al4V alloys with 60%-70% porosity have potential for cortical bone implant applications.
文摘The performance of gas diffusion porous electrode starved of electrolyte solution can be significantly increased by decreasing the thickness of uneven liquid film covering the catalyst agglomerates.
基金Supported by the National Natural Science Foundation of China under Grant No 51176044the Natural Science Foundation of Zhejiang Province under Grant No LY13A040007the China Postdoctoral Science Foundation under Grant Nos 2013M541634and 2014T70498
文摘A coarse-grained model is proposed to study the dynamics of a nano-chain diffusing in porous media. The simulation utilizes a hybrid method which combines stochastic rotation dynamics with molecular dynamics. Solvent molecules are explicitly taken into account to represent the hydrodynamic interactions and random fluctuations. The conformation, relaxation, and diffusion properties of a polymer chain are investigated by changing the density degree of the obstacle matrix. It is found that the average size of the chain is a non- monotonic function of the obstacle volume faction Ф. A dense environment may contribute to extending a linear chain, which can be characterized by larger exponents in the corresponding power law. The relaxation behavior of a stretched chain to a steady state shows dramatic crossover from exponent to power-law relaxation when the values of φ are increased. The dependence of the diffusion coefficient on the chain size is also studied. Various kinds of scaling properties are presented and discussed. The results can give additional insight into the density effect of porous media on polymer structure and dynamics.
基金Project(2014CB643404)supported by the National Basic Research Program of ChinaProject(51374254)supported by the National Natural Science Foundation of China
文摘The leaching kinetics of zinc silicate in ammonium chloride solution was investigated. The effects of stirring speed （150？400 r/min）, leaching temperature （95-108 ℃, particle size of zinc silicate （61-150 μm） and the concentration of ammonium chloride （3.5-5.5 mol/L） on leaching rate of zinc were studied. The results show that decreasing the particle size of zinc silicate and increasing the leaching temperature and concentration of ammonium chloride can obviously enhance the leaching rate of zinc. Among the kinetic models of the porous solids tested, the grain model with porous diffusion control can well describe the zinc leaching kinetics. The apparent activation energy of the leaching reaction is 161.26 kJ/mol and the reaction order with respect to ammonium chloride is 3.5.
文摘This paper studies the unsteady heat and mass natural convection in a highly porous medium bounded by an infinite vertical porous wall. The unsteady source of the problem arises from the transverse oscillations in suction velocity of fluids, The analytical results for the problem are obtained based on the method of small parameter, and show that the natural circulation in the porous medium is affected by this kind of oscillation.
基金Supported by Guangdong Basic and Applied Basic Research Foundation(Grant No.2021A1515010336),NSFC(Grant Nos.12271186,12171166)。
文摘In this paper,we deal with the following chemotaxis-haptotaxis system modeling cancer invasion with nonlinear diffusion,ut=Δum−χ∇·(u∇v)−ξ∇·(u∇ω)+μu(1−u−ω),inΩ×R^(+),vt−Δv+v=u,inΩ×R+,ωt=−vω,inΩ×R+,whereΩ⊂R^(N)is a bounded domain.We first supplement the results of global existence and uniform boundedness of solutions for the case m=2N N+2.Then for any m>0 and any spatial dimension,we consider the stability of equilibrium,and find that the chemotaxis has a destabilizing effect,that is for the ODEs,or the diffusion-ODE system without chemotaxis,the solutions tend to a linearly stable uniform steady state(1,1,0).When the chemotactic coefficientχis large,the equilibrium(1,1,0)become unstable.Then we study the existence of nontrivial stationary solutions via bifurcation techniques withχbeing the bifurcation parameter,and obtain nonhomogeneous patterns.At last,we also investigate the stability of these bifurcation solutions.
文摘We study in this paper the first boundary value problem of one dimensional degenerate quasilinear elliptic-parabolic equation with discontinuous coefficients (layered media). The uniquenessof the weak solutions is proved under natural conditions.
