为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立...为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立相应的预测模型.针对粗加工与精加工的不同加工目标,利用第二代非支配排序遗传算法(NSGA-Ⅱ)结合熵权法与逼近理想解的排序方法即熵权TOPSIS(technique for order proference by similarity to ideal solution)法进行了多目标磨削工艺参数优化,并进行验证.结果表明:粗加工磨削参数采用a_(p)=53.61μm,v_(s)=29.99 m/s,v_(w)=311.89 mm/min;精加工磨削参数采用ap=14.96μm,v_(s)=29.99 m/s,v_(w)=300.92 mm/min.经两道工序加工,表面粗糙度标准差从0.195μm降至0.101μm,有效提高NiCo-FGMs的表面粗糙度一致性.展开更多
The article introduces a finite element procedure using the bilinear quadrilateral element or four-node rectangular element(namely Q4 element) based on a refined first-order shear deformation theory(rFSDT) and Monte C...The article introduces a finite element procedure using the bilinear quadrilateral element or four-node rectangular element(namely Q4 element) based on a refined first-order shear deformation theory(rFSDT) and Monte Carlo simulation(MCS), so-called refined stochastic finite element method to investigate the random vibration of functionally graded material(FGM) plates subjected to the moving load.The advantage of the proposed method is to use r-FSDT to improve the accuracy of classical FSDT, satisfy the stress-free condition at the plate boundaries, and combine with MCS to analyze the vibration of the FGM plate when the parameter inputs are random quantities following a normal distribution. The obtained results show that the distribution characteristics of the vibration response of the FGM plate depend on the standard deviation of the input parameters and the velocity of the moving load.Furthermore, the numerical results in this study are expected to contribute to improving the understanding of FGM plates subjected to moving loads with uncertain input parameters.展开更多
通过对益生菌FGM所产α-半乳糖苷酶aga2基因在黄芪发酵不同阶段的表达水平分析,为α-半乳糖苷酶在黄芪发酵过程中的作用及其益生机制探究提供依据。绘制益生菌FGM在黄芪发酵过程中的生长及发酵液pH变化曲线,同源序列法克隆aga2基因,运用...通过对益生菌FGM所产α-半乳糖苷酶aga2基因在黄芪发酵不同阶段的表达水平分析,为α-半乳糖苷酶在黄芪发酵过程中的作用及其益生机制探究提供依据。绘制益生菌FGM在黄芪发酵过程中的生长及发酵液pH变化曲线,同源序列法克隆aga2基因,运用SYBR Green I实时荧光定量PCR技术检测aga2基因在黄芪发酵不同阶段表达水平。结果表明,在发酵6h内FGM菌株处于对数生长期,大量产酸使pH由初始7.2迅速下降到5.3;12h后细菌进入稳定期,pH下降到4.5;48h至发酵结束pH稳定在4.0左右。成功克隆到一段648bp的aga2基因片段(GenBank登录号KC202825),序列相似性最高达98%。发酵24h内aga2基因表达逐渐上调并达到最高;36h表达水平下降明显,仅是初始发酵水平的1.28倍,之后至60h又呈上升趋势。上述结果提示,益生菌FGM在黄芪发酵中可产生α-半乳糖苷酶以分解黄芪粉中的抗营养因子α-半乳糖苷类,其分解产物半乳糖通过Leloir途径中间产物UDP-半乳糖可能间接参与胞外多糖合成,为黄芪发酵产物中多糖得率增加起了一定作用。展开更多
文摘为解决激光定向能量沉积(laser-directed energy deposition,L-DED)成型工艺制备的镍钴基功能梯度材料(NiCo-FGMs)磨削后表面质量一致性较差这一问题,基于正交试验分析了磨削工艺参数对NiCo-FGMs的磨削力和表面粗糙度的影响规律,并建立相应的预测模型.针对粗加工与精加工的不同加工目标,利用第二代非支配排序遗传算法(NSGA-Ⅱ)结合熵权法与逼近理想解的排序方法即熵权TOPSIS(technique for order proference by similarity to ideal solution)法进行了多目标磨削工艺参数优化,并进行验证.结果表明:粗加工磨削参数采用a_(p)=53.61μm,v_(s)=29.99 m/s,v_(w)=311.89 mm/min;精加工磨削参数采用ap=14.96μm,v_(s)=29.99 m/s,v_(w)=300.92 mm/min.经两道工序加工,表面粗糙度标准差从0.195μm降至0.101μm,有效提高NiCo-FGMs的表面粗糙度一致性.
文摘The article introduces a finite element procedure using the bilinear quadrilateral element or four-node rectangular element(namely Q4 element) based on a refined first-order shear deformation theory(rFSDT) and Monte Carlo simulation(MCS), so-called refined stochastic finite element method to investigate the random vibration of functionally graded material(FGM) plates subjected to the moving load.The advantage of the proposed method is to use r-FSDT to improve the accuracy of classical FSDT, satisfy the stress-free condition at the plate boundaries, and combine with MCS to analyze the vibration of the FGM plate when the parameter inputs are random quantities following a normal distribution. The obtained results show that the distribution characteristics of the vibration response of the FGM plate depend on the standard deviation of the input parameters and the velocity of the moving load.Furthermore, the numerical results in this study are expected to contribute to improving the understanding of FGM plates subjected to moving loads with uncertain input parameters.
文摘通过对益生菌FGM所产α-半乳糖苷酶aga2基因在黄芪发酵不同阶段的表达水平分析,为α-半乳糖苷酶在黄芪发酵过程中的作用及其益生机制探究提供依据。绘制益生菌FGM在黄芪发酵过程中的生长及发酵液pH变化曲线,同源序列法克隆aga2基因,运用SYBR Green I实时荧光定量PCR技术检测aga2基因在黄芪发酵不同阶段表达水平。结果表明,在发酵6h内FGM菌株处于对数生长期,大量产酸使pH由初始7.2迅速下降到5.3;12h后细菌进入稳定期,pH下降到4.5;48h至发酵结束pH稳定在4.0左右。成功克隆到一段648bp的aga2基因片段(GenBank登录号KC202825),序列相似性最高达98%。发酵24h内aga2基因表达逐渐上调并达到最高;36h表达水平下降明显,仅是初始发酵水平的1.28倍,之后至60h又呈上升趋势。上述结果提示,益生菌FGM在黄芪发酵中可产生α-半乳糖苷酶以分解黄芪粉中的抗营养因子α-半乳糖苷类,其分解产物半乳糖通过Leloir途径中间产物UDP-半乳糖可能间接参与胞外多糖合成,为黄芪发酵产物中多糖得率增加起了一定作用。
