Solution heat treatment combined with a rapid quenching operation,which can effectively suppress the decomposition of the supersaturated solid solution in the matrix,is a vital process step for producing large precipi...Solution heat treatment combined with a rapid quenching operation,which can effectively suppress the decomposition of the supersaturated solid solution in the matrix,is a vital process step for producing large precipitation-hardenable aluminum alloy thick plates with desired properties.However,large thermal gradients that result from the non-uniform cooling rates during quenching usually give rise to severely heterogeneous distributions of residual stress in thick plates.The presence of roller-hearth furnaces makes it possible to achieve continuous and integral solution-quenching treatment for large aluminum alloy thick plates.The conveyor velocity of the roller table in the roller-hearth furnace is a key parameter but its influence is less addressed in literature.Thus,in the present work,finite element thermal-mechanical simulations taking into account different conveyor velocities of the roller table were employed to predict the temperature variations and residual stress distributions in large aluminum alloy thick plates during quenching process.Four different velocities were utilized in the simulations.The modeling results showed that the temperature evolutions as well as the distributions of the induced internal stresses in those large thick plates during quenching treatments were indeed affected by the conveyor velocities.Slower velocities were demonstrated to be favorable for gaining thick plates being with relatively homogeneous residual stress distributions in the plates.展开更多
Taking a published natural population life table of rice leaf roller, Cnaphalocrocis medinalis （Lepidoptera： Pyralidae）, as an example, we estimated the population trend index, I, via re-sampling methods （jackknif...Taking a published natural population life table of rice leaf roller, Cnaphalocrocis medinalis （Lepidoptera： Pyralidae）, as an example, we estimated the population trend index, I, via re-sampling methods （jackknife and bootstrap）, determined its statistical properties and illustrated the application of these methods in determining the control effectiveness of bio- agents and chemical insecticides. Depending on the simulation outputs, the smoothed distribution pattern of the estimates of I by delete-1 jackknife is visually distinguishable from the normal density, but the smoothed pattern produced by delete-d jackknife, and logarithm- transformed smoothed patterns produced by both empirical and parametric bootstraps, matched well the corresponding normal density. Thus, the estimates of I produced by delete-1 jackknife were not used to determine the suppressive effect of wasps and insecticides. The 95% percent confidence intervals or the narrowest 95 percentiles and Z-test criterion were employed to compare the effectiveness of Trichogrammajaponicum Ashmead and insecticides （powder, 1.5% mevinphos ＋ 3% alpha-hexachloro cyclohexane） against the rice leaf roller based on the estimates of I produced by delete-d jackknife and bootstrap techniques. At a = 0.05 level, there were statistical differences between wasp treatment and control, and between wasp and insecticide treatments, if the normality is ensured, or by the narrowest 95 percentiles. However, there is still no difference between insecticide treatment and control. By Z-test criterion, wasp treatment is better than control and insecticide treatment with P-value 〈 0.01. Insecticide treatment is similar to control with P-value 〉 0.2 indicating that 95% confidence intervals procedure is more conservative. Although similar conclusions may be drawn by re-sampling techniques, such as the delta method, about the suppressive effect of trichogramma and insecticides, the normality of the estimates can be checked and guaranteed, and the correlation among sequential life stages of rice leaf roller is also considered in the estimation. Judged by the P-values from Z-test, the delta method is more conservative.展开更多
基金National Program on Key Research and Development Project of China(No.2020YFF0218202)Innovation Fund Project of GRINM Group Co.,Ltd。
文摘Solution heat treatment combined with a rapid quenching operation,which can effectively suppress the decomposition of the supersaturated solid solution in the matrix,is a vital process step for producing large precipitation-hardenable aluminum alloy thick plates with desired properties.However,large thermal gradients that result from the non-uniform cooling rates during quenching usually give rise to severely heterogeneous distributions of residual stress in thick plates.The presence of roller-hearth furnaces makes it possible to achieve continuous and integral solution-quenching treatment for large aluminum alloy thick plates.The conveyor velocity of the roller table in the roller-hearth furnace is a key parameter but its influence is less addressed in literature.Thus,in the present work,finite element thermal-mechanical simulations taking into account different conveyor velocities of the roller table were employed to predict the temperature variations and residual stress distributions in large aluminum alloy thick plates during quenching process.Four different velocities were utilized in the simulations.The modeling results showed that the temperature evolutions as well as the distributions of the induced internal stresses in those large thick plates during quenching treatments were indeed affected by the conveyor velocities.Slower velocities were demonstrated to be favorable for gaining thick plates being with relatively homogeneous residual stress distributions in the plates.
文摘Taking a published natural population life table of rice leaf roller, Cnaphalocrocis medinalis （Lepidoptera： Pyralidae）, as an example, we estimated the population trend index, I, via re-sampling methods （jackknife and bootstrap）, determined its statistical properties and illustrated the application of these methods in determining the control effectiveness of bio- agents and chemical insecticides. Depending on the simulation outputs, the smoothed distribution pattern of the estimates of I by delete-1 jackknife is visually distinguishable from the normal density, but the smoothed pattern produced by delete-d jackknife, and logarithm- transformed smoothed patterns produced by both empirical and parametric bootstraps, matched well the corresponding normal density. Thus, the estimates of I produced by delete-1 jackknife were not used to determine the suppressive effect of wasps and insecticides. The 95% percent confidence intervals or the narrowest 95 percentiles and Z-test criterion were employed to compare the effectiveness of Trichogrammajaponicum Ashmead and insecticides （powder, 1.5% mevinphos ＋ 3% alpha-hexachloro cyclohexane） against the rice leaf roller based on the estimates of I produced by delete-d jackknife and bootstrap techniques. At a = 0.05 level, there were statistical differences between wasp treatment and control, and between wasp and insecticide treatments, if the normality is ensured, or by the narrowest 95 percentiles. However, there is still no difference between insecticide treatment and control. By Z-test criterion, wasp treatment is better than control and insecticide treatment with P-value 〈 0.01. Insecticide treatment is similar to control with P-value 〉 0.2 indicating that 95% confidence intervals procedure is more conservative. Although similar conclusions may be drawn by re-sampling techniques, such as the delta method, about the suppressive effect of trichogramma and insecticides, the normality of the estimates can be checked and guaranteed, and the correlation among sequential life stages of rice leaf roller is also considered in the estimation. Judged by the P-values from Z-test, the delta method is more conservative.
