3D microstructures of Fe–6.5%Si(mass fraction) alloys prepared under different cooling conditions were simulated via finite element-cellular automaton(CAFE) method. The simulated results were compared to experimental...3D microstructures of Fe–6.5%Si(mass fraction) alloys prepared under different cooling conditions were simulated via finite element-cellular automaton(CAFE) method. The simulated results were compared to experimental results and found to be in accordance. Variations in the temperature field and solid-liquid region, which plays important roles in determining solidification structures, were also examined under various cooling conditions. The proposed model was utilized to determine the effects of Gaussian distribution parameters to find that the lower the mean undercooling, the higher the equiaxed crystal zone ratio; also, the larger the maximum nucleation density, the smaller the grain size. The influence of superheat on solidification structure and columnar to equiaxed transition(CET) in the cast ingot was also investigated to find that decrease in superheat from 52 K to 20 K causes the equiaxed crystal zone ratio to increase from 58.13% to 65.6%, the mean gain radius to decrease from 2.102 mm to 1.871 mm, and the CET to occur ahead of schedule. To this effect, low superheat casting is beneficial to obtain finer equiaxed gains and higher equiaxed dendrite zone ratio in Fe–6.5%Si alloy cast ingots.展开更多
Effects of magnesia fines addition （ 4%, 6% and 8% in mass ） and spinel with different compositions （alumina-rich, magnesia-rich and stoichiometric spi-nel） on thermal expansion behavior of alumina magne-sia casta...Effects of magnesia fines addition （ 4%, 6% and 8% in mass ） and spinel with different compositions （alumina-rich, magnesia-rich and stoichiometric spi-nel） on thermal expansion behavior of alumina magne-sia castables were researched using tabular corundum, magnesia fines, spinel fines, p-A12O3, Secar-71 cement and SiO2 fume as main starting materials. The results show that： （1） thermal expansion coefficients of speci- mens with 4 mass% and 6 mass% magnesia fines have the similar change tendency, increasing slightly with temperature rising ; when magnesia addition is 8 mass% , the thermal expansion coefficient increases ob-viously at Ⅰ 050 ℃ and reaches the peak at 1 350 ℃ ; （2） when MgO content is the same, the specimen with magnesia-rich spinel has the lowest thermal expansion coefficient; （3） for the castables specimens with the same MgO content, the specimen with magnesia has higher thermal expansion coefficient than that with pre-synthesized spin, el, which is related with the secondary spinelization dttriag the heating process.展开更多
Effect of different particle sizes of cordierite on properties of castable refractory by different heat treatment temperatures were investigated respectively with mullite and bauxite as raw materials, calcium aluminat...Effect of different particle sizes of cordierite on properties of castable refractory by different heat treatment temperatures were investigated respectively with mullite and bauxite as raw materials, calcium aluminate cement as binders. After 24 h curing in mould and another 24 h curing at 110 ℃ after demoulding, the specimens were heat treated at 1 000 ℃, 1 300℃ and 1 500℃ for 3 h, respectively. The bulk density （ BD）, permanent linear change （ PLC）, modulus of rupture（MOR） and clod crushing strength（CCS）, thermal expansion coefficient and thermal shock resistance were examined. The results show that there is no obvious effect on adjusting permanent linear change and bulk density of castables by adding different particle sizes of cordierite at low temperature and intermediate temperature. Modulus of rupture of castable increase with the decreasing of the particle sizes of cordierite after heat treated by 1 000 ℃ and 1 300℃. In this experiment, thermal shock resistance of the castable with cordierite whose particle size is 0 - 1 mm is the best.展开更多
In this paper, considering the different elastic properties in the attached head and the free head, we propose a physical model, in which the free head undergoes a diffusive search in an entropic spring potential form...In this paper, considering the different elastic properties in the attached head and the free head, we propose a physical model, in which the free head undergoes a diffusive search in an entropic spring potential formed by undocking the neck linker, and there are asymmetric conformational changes in the attached head formed by docking the neck linker to support the load force and bias the diffusive search to the forward direction. By performing the thermodynamic analysis, we obtain the free energy difference between forward and backward binding sites. And using the Fokker-Planck equation with two absorbing boundaries, we obtain the dependence of the ratio of forward to backward steps on the backward force. Also, within the Michaelis-Menten model, we investigate the dependence of the velocity-load relationship on the effective length of the junction between the two heads. The results show that our model can provide a physical understanding for the processive movement of kinesin.展开更多
基金Project(2012AA03A505)supported by the High-Tech Research and Development Program of ChinaProject(51474023)supported by the National Natural Science Foundation of China
文摘3D microstructures of Fe–6.5%Si(mass fraction) alloys prepared under different cooling conditions were simulated via finite element-cellular automaton(CAFE) method. The simulated results were compared to experimental results and found to be in accordance. Variations in the temperature field and solid-liquid region, which plays important roles in determining solidification structures, were also examined under various cooling conditions. The proposed model was utilized to determine the effects of Gaussian distribution parameters to find that the lower the mean undercooling, the higher the equiaxed crystal zone ratio; also, the larger the maximum nucleation density, the smaller the grain size. The influence of superheat on solidification structure and columnar to equiaxed transition(CET) in the cast ingot was also investigated to find that decrease in superheat from 52 K to 20 K causes the equiaxed crystal zone ratio to increase from 58.13% to 65.6%, the mean gain radius to decrease from 2.102 mm to 1.871 mm, and the CET to occur ahead of schedule. To this effect, low superheat casting is beneficial to obtain finer equiaxed gains and higher equiaxed dendrite zone ratio in Fe–6.5%Si alloy cast ingots.
文摘Effects of magnesia fines addition （ 4%, 6% and 8% in mass ） and spinel with different compositions （alumina-rich, magnesia-rich and stoichiometric spi-nel） on thermal expansion behavior of alumina magne-sia castables were researched using tabular corundum, magnesia fines, spinel fines, p-A12O3, Secar-71 cement and SiO2 fume as main starting materials. The results show that： （1） thermal expansion coefficients of speci- mens with 4 mass% and 6 mass% magnesia fines have the similar change tendency, increasing slightly with temperature rising ; when magnesia addition is 8 mass% , the thermal expansion coefficient increases ob-viously at Ⅰ 050 ℃ and reaches the peak at 1 350 ℃ ; （2） when MgO content is the same, the specimen with magnesia-rich spinel has the lowest thermal expansion coefficient; （3） for the castables specimens with the same MgO content, the specimen with magnesia has higher thermal expansion coefficient than that with pre-synthesized spin, el, which is related with the secondary spinelization dttriag the heating process.
文摘Effect of different particle sizes of cordierite on properties of castable refractory by different heat treatment temperatures were investigated respectively with mullite and bauxite as raw materials, calcium aluminate cement as binders. After 24 h curing in mould and another 24 h curing at 110 ℃ after demoulding, the specimens were heat treated at 1 000 ℃, 1 300℃ and 1 500℃ for 3 h, respectively. The bulk density （ BD）, permanent linear change （ PLC）, modulus of rupture（MOR） and clod crushing strength（CCS）, thermal expansion coefficient and thermal shock resistance were examined. The results show that there is no obvious effect on adjusting permanent linear change and bulk density of castables by adding different particle sizes of cordierite at low temperature and intermediate temperature. Modulus of rupture of castable increase with the decreasing of the particle sizes of cordierite after heat treated by 1 000 ℃ and 1 300℃. In this experiment, thermal shock resistance of the castable with cordierite whose particle size is 0 - 1 mm is the best.
文摘In this paper, considering the different elastic properties in the attached head and the free head, we propose a physical model, in which the free head undergoes a diffusive search in an entropic spring potential formed by undocking the neck linker, and there are asymmetric conformational changes in the attached head formed by docking the neck linker to support the load force and bias the diffusive search to the forward direction. By performing the thermodynamic analysis, we obtain the free energy difference between forward and backward binding sites. And using the Fokker-Planck equation with two absorbing boundaries, we obtain the dependence of the ratio of forward to backward steps on the backward force. Also, within the Michaelis-Menten model, we investigate the dependence of the velocity-load relationship on the effective length of the junction between the two heads. The results show that our model can provide a physical understanding for the processive movement of kinesin.
