A numerical simulation of the interaction between laminar flow with low Reynolds number and a highly flexible elastic sheet is presented. The mathematical model for the simulation includes a three-dimensional finitevo...A numerical simulation of the interaction between laminar flow with low Reynolds number and a highly flexible elastic sheet is presented. The mathematical model for the simulation includes a three-dimensional finitevolume based fluid solver for incompressible viscous flow and a combined finite-discrete element method for the three-dimensional deformation of solid. An immersed boundary method is used to couple the simulation of fluid and solid. It is implemented through a set of immersed boundary points scattered on the solid surface. These points provide a deformable solid wall boundary for the fluid by adding body force to Navier-Stokes equations. The force from the fluid is also obtained for each point and then applied on the boundary nodes of the solid. The vortex-induced vibration of the highly flexible elastic sheet is simulated with the established mathematical model. The simulated results for both swing pattern and oscillation frequency of the elastic sheet in low Reynolds number flow agree well with experimental data.展开更多
The interaction between screw dislocations and two asymmetrical interfacial cracks emanating from an elliptic hole under loads at infinity is studied. The closed-form solution is derived for complex potentials. The st...The interaction between screw dislocations and two asymmetrical interfacial cracks emanating from an elliptic hole under loads at infinity is studied. The closed-form solution is derived for complex potentials. The stress intensity factor and the critical applied stress for the dislocation emission are also calculated. In the limiting cases, well-known results can be obtained from the present solutions. Moreover, new exact solutions for a screw dislocation interacting with some complicated cracks are derived. The results show that the shielding effect increases with the increase in the length of the other cracks and the minor semi axis, but decreases with the increase of dislocation azimuth. The repulsion acting on the dislocation from the other phase and the other crack extend in the horizontal direction, which makes the dislocation emission at the crack tip take place more easily, but the minor semi axis of the elliptical hole extending in the vertical direction makes it more difficult.展开更多
Ca_(5)Nb_(4)TiO_(17) ceramics with 0≤x≤0.4 were prepared through a solid-state reaction method.Effects of zinc substitution on sintering behavior and microwave dielectric properties of Ca_(5)Nb_(4)TiO_(17) ceramics ...Ca_(5)Nb_(4)TiO_(17) ceramics with 0≤x≤0.4 were prepared through a solid-state reaction method.Effects of zinc substitution on sintering behavior and microwave dielectric properties of Ca_(5)Nb_(4)TiO_(17) ceramics were investigated.The sintering temperature was significantly lowered from 1480℃for pure Ca_(5)Nb_(4)TiO_(17) to 1260℃ for x=0.4.The microwave dielectric properties are strongly correlated with the composition.It is worth noting that the temperature cofficient of resonant frequency(τf)displays a tendency toward positive value,ranging from-126.4 ppm/℃ to-8.6 ppm/℃.A temperature stable microwave ceramic with dielectric constant of 52 and Q×f value of 9937GHz is achieved at x=0.4 and is a potential candidate for application as cores in dielectrically loaded antennas.展开更多
A series of ceramics with a general formula,La_(2)Ti_(2-x)Ta_(x)O_(7),in which x=0.05;0.1;0.2;and 0.3,were prepared by Spark Plasma Sintering(SPS).Effects of tantalum substitution for titanium on the structure,dielect...A series of ceramics with a general formula,La_(2)Ti_(2-x)Ta_(x)O_(7),in which x=0.05;0.1;0.2;and 0.3,were prepared by Spark Plasma Sintering(SPS).Effects of tantalum substitution for titanium on the structure,dielectric,and piezoelectric properties were studied.Results revealed that the structure changed gradually from 4-layer to 3-layer due to the higher valence of Ta.The solid solution limit of tantalum in La_(2)Ti_(2)O_(7)lattice was in the proximity of x=0.2.The ferroelectric Curie temperature(Tc)decreased with increasing tantalum doping content.dc resistivity reached a maximum value at x=0.2 with a value of~1.0×10^(8)Ωcm at 600℃.The influence of texture on the piezoelectric properties of La_(2)Ti_(2-x)Ta_(x)O_(7)ceramics was also investigated.A maximum d_(33)value~2:1 pC/N was obtained at x=0.2.展开更多
基金Supported by Marie Curie International Incoming Fellowship (No. PIIF-GA-2009-253453)
文摘A numerical simulation of the interaction between laminar flow with low Reynolds number and a highly flexible elastic sheet is presented. The mathematical model for the simulation includes a three-dimensional finitevolume based fluid solver for incompressible viscous flow and a combined finite-discrete element method for the three-dimensional deformation of solid. An immersed boundary method is used to couple the simulation of fluid and solid. It is implemented through a set of immersed boundary points scattered on the solid surface. These points provide a deformable solid wall boundary for the fluid by adding body force to Navier-Stokes equations. The force from the fluid is also obtained for each point and then applied on the boundary nodes of the solid. The vortex-induced vibration of the highly flexible elastic sheet is simulated with the established mathematical model. The simulated results for both swing pattern and oscillation frequency of the elastic sheet in low Reynolds number flow agree well with experimental data.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11172094 and 11172095)the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-11-0122)+1 种基金the Science Fund of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, China (Grant Nos. 61075005 and 51075001)the Fundamental Research Funds for the Central Universities (Hunan University), China
文摘The interaction between screw dislocations and two asymmetrical interfacial cracks emanating from an elliptic hole under loads at infinity is studied. The closed-form solution is derived for complex potentials. The stress intensity factor and the critical applied stress for the dislocation emission are also calculated. In the limiting cases, well-known results can be obtained from the present solutions. Moreover, new exact solutions for a screw dislocation interacting with some complicated cracks are derived. The results show that the shielding effect increases with the increase in the length of the other cracks and the minor semi axis, but decreases with the increase of dislocation azimuth. The repulsion acting on the dislocation from the other phase and the other crack extend in the horizontal direction, which makes the dislocation emission at the crack tip take place more easily, but the minor semi axis of the elliptical hole extending in the vertical direction makes it more difficult.
基金'ChuYing' Program of Southwest Jiaotong University and Thousand Talents Program of Sichuan Province.Also,we thank for the supports of National Natural Science Foundation of China，Grant-in-Aid for Scientific Research B (No.23350104) from Japan Society for the Promotion Science,the Fundamental Research Program of Korean Institute of Materials Science，UK EPSRC Material Systems for Extreme Environments Programme Grant
基金supported by the National Basic Research Program of China(2009CB623306)International Science&Technology Cooperation Program of China(2013DFR50470).
文摘Ca_(5)Nb_(4)TiO_(17) ceramics with 0≤x≤0.4 were prepared through a solid-state reaction method.Effects of zinc substitution on sintering behavior and microwave dielectric properties of Ca_(5)Nb_(4)TiO_(17) ceramics were investigated.The sintering temperature was significantly lowered from 1480℃for pure Ca_(5)Nb_(4)TiO_(17) to 1260℃ for x=0.4.The microwave dielectric properties are strongly correlated with the composition.It is worth noting that the temperature cofficient of resonant frequency(τf)displays a tendency toward positive value,ranging from-126.4 ppm/℃ to-8.6 ppm/℃.A temperature stable microwave ceramic with dielectric constant of 52 and Q×f value of 9937GHz is achieved at x=0.4 and is a potential candidate for application as cores in dielectrically loaded antennas.
基金supported by the National Basic Research Program of China(2009CB623306)International Science&Technology Cooperation Program of China(2013DFR50470)China Scholarship Council。
文摘A series of ceramics with a general formula,La_(2)Ti_(2-x)Ta_(x)O_(7),in which x=0.05;0.1;0.2;and 0.3,were prepared by Spark Plasma Sintering(SPS).Effects of tantalum substitution for titanium on the structure,dielectric,and piezoelectric properties were studied.Results revealed that the structure changed gradually from 4-layer to 3-layer due to the higher valence of Ta.The solid solution limit of tantalum in La_(2)Ti_(2)O_(7)lattice was in the proximity of x=0.2.The ferroelectric Curie temperature(Tc)decreased with increasing tantalum doping content.dc resistivity reached a maximum value at x=0.2 with a value of~1.0×10^(8)Ωcm at 600℃.The influence of texture on the piezoelectric properties of La_(2)Ti_(2-x)Ta_(x)O_(7)ceramics was also investigated.A maximum d_(33)value~2:1 pC/N was obtained at x=0.2.
