为了保证永磁无刷直流空心轴电机的输出性能和抑制电磁振动,提出了一种基于非线性多元回归的修正代理模型优化方法.首先,通过AE(Audze-Elglajs)准则确定最优空间填充抽样,并采用核主成分分析(Kernel Principal Components Analysis,KPCA...为了保证永磁无刷直流空心轴电机的输出性能和抑制电磁振动,提出了一种基于非线性多元回归的修正代理模型优化方法.首先,通过AE(Audze-Elglajs)准则确定最优空间填充抽样,并采用核主成分分析(Kernel Principal Components Analysis,KPCA)算法筛选出4个主要变量用于构建代理模型;其次,采用非线性多元回归构建代理模型,决定系数R^(2)值均大于0.9,验证了代理模型的精度;最后,采用鲁棒多目标遗传算法求解代理模型,获得了最优定子槽参数.结果表明,通过优化定子槽参数,电机平均转矩降低了1.3%,不影响输出性能,电机空载、额定负载时最大振动加速度分别降低19%和34.5%,有效地降低了电磁振动,验证了优化方法的有效性和可靠性.展开更多
Polycaprolactone/hydroxyapatite(PCL/HA)composite coating was fabricated by a combination of hydrothermal and dipping methods to delay the degradation of Mg alloy AZ31 as bioresorbable materials.The PCL/HA coating was ...Polycaprolactone/hydroxyapatite(PCL/HA)composite coating was fabricated by a combination of hydrothermal and dipping methods to delay the degradation of Mg alloy AZ31 as bioresorbable materials.The PCL/HA coating was composed of nano rod-shape HA crystals and PCL filled in the space of HA crystals.Compared with the single HA coating,the binding strength between the PCL/HA composite coating and Mg alloy was obviously improved and the PCL/HA coating still adhered to the surface of AZ31 substrate even after 38 days of immersion.The electrochemical corrosion rate of HA coated sample was reduced by ten times after being filled by PCL.The electrochemical impedance spectroscopy(EIS)and immersion test results showed that the PCL/HA composite coating could provide a more effective barrier for Mg substrate than the HA coating alone.The cytocompatibility and the antibacterial property of HA coating and PCL/HA coating were evaluated by culturing with bone marrow-derived mesenchymal stem cells(BMSCs)and methicillin-resistant staphylococcus aureus(MRSA)for 24 h under direct culture conditions,respectively.The PCL/HA composite coating showed better BMSC cell compatibility,more suitable for BMSC adhesion than HA coating alone and showed a potential application prospect as a biological materials.However,from the perspective of clinical applications,the antibacterial property of PCL/HA composite coating needs to be further improved.展开更多
文中介绍了一种新型环保绝缘气体六氟丙烯(1-C_(3)F_(6)),并重点研究了1-C_(3)F_(6)与CO_(2)混合气体在不同电极结构和电压特性下的绝缘特性。研究表明:在均匀电场中,1-C_(3)F_(6)/CO_(2)混合气体的50%击穿电压随着电极间距、气压的增...文中介绍了一种新型环保绝缘气体六氟丙烯(1-C_(3)F_(6)),并重点研究了1-C_(3)F_(6)与CO_(2)混合气体在不同电极结构和电压特性下的绝缘特性。研究表明:在均匀电场中,1-C_(3)F_(6)/CO_(2)混合气体的50%击穿电压随着电极间距、气压的增加而增加,工频击穿电压随着充气压力的升高而近似线性升高,纯1-C_(3)F_(6)气体在1.25 bar(1 bar=100 k Pa)时的工频击穿电压与SF_(6)接近。此外,在各个充气压力下,1-C_(3)F_(6)/CO_(2)混合气体的工频击穿电压都比C_(5)F_(10)O/Air混合气体高。在稍不均匀电场中,1-C_(3)F_(6)/CO_(2)混合气体直流和工频击穿电压随着充气压力的升高而升高,表现出较好的线性度。在极不均匀电场下,1-C_(3)F_(6)/CO_(2)混合气体工频击穿电压随着充气压力的升高而缓慢升高,逐渐趋于饱和。文中的试验结果可以为电力产品设计提供参考和依据。展开更多
文摘为了保证永磁无刷直流空心轴电机的输出性能和抑制电磁振动,提出了一种基于非线性多元回归的修正代理模型优化方法.首先,通过AE(Audze-Elglajs)准则确定最优空间填充抽样,并采用核主成分分析(Kernel Principal Components Analysis,KPCA)算法筛选出4个主要变量用于构建代理模型;其次,采用非线性多元回归构建代理模型,决定系数R^(2)值均大于0.9,验证了代理模型的精度;最后,采用鲁棒多目标遗传算法求解代理模型,获得了最优定子槽参数.结果表明,通过优化定子槽参数,电机平均转矩降低了1.3%,不影响输出性能,电机空载、额定负载时最大振动加速度分别降低19%和34.5%,有效地降低了电磁振动,验证了优化方法的有效性和可靠性.
基金supported by the National Natural Science Foundation of China[Grant No.51201192]Natural Science Foundation of Chongqing[Grant No.cstc2018jcyj A2285cstc2018jcyjA 2285]。
文摘Polycaprolactone/hydroxyapatite(PCL/HA)composite coating was fabricated by a combination of hydrothermal and dipping methods to delay the degradation of Mg alloy AZ31 as bioresorbable materials.The PCL/HA coating was composed of nano rod-shape HA crystals and PCL filled in the space of HA crystals.Compared with the single HA coating,the binding strength between the PCL/HA composite coating and Mg alloy was obviously improved and the PCL/HA coating still adhered to the surface of AZ31 substrate even after 38 days of immersion.The electrochemical corrosion rate of HA coated sample was reduced by ten times after being filled by PCL.The electrochemical impedance spectroscopy(EIS)and immersion test results showed that the PCL/HA composite coating could provide a more effective barrier for Mg substrate than the HA coating alone.The cytocompatibility and the antibacterial property of HA coating and PCL/HA coating were evaluated by culturing with bone marrow-derived mesenchymal stem cells(BMSCs)and methicillin-resistant staphylococcus aureus(MRSA)for 24 h under direct culture conditions,respectively.The PCL/HA composite coating showed better BMSC cell compatibility,more suitable for BMSC adhesion than HA coating alone and showed a potential application prospect as a biological materials.However,from the perspective of clinical applications,the antibacterial property of PCL/HA composite coating needs to be further improved.
文摘文中介绍了一种新型环保绝缘气体六氟丙烯(1-C_(3)F_(6)),并重点研究了1-C_(3)F_(6)与CO_(2)混合气体在不同电极结构和电压特性下的绝缘特性。研究表明:在均匀电场中,1-C_(3)F_(6)/CO_(2)混合气体的50%击穿电压随着电极间距、气压的增加而增加,工频击穿电压随着充气压力的升高而近似线性升高,纯1-C_(3)F_(6)气体在1.25 bar(1 bar=100 k Pa)时的工频击穿电压与SF_(6)接近。此外,在各个充气压力下,1-C_(3)F_(6)/CO_(2)混合气体的工频击穿电压都比C_(5)F_(10)O/Air混合气体高。在稍不均匀电场中,1-C_(3)F_(6)/CO_(2)混合气体直流和工频击穿电压随着充气压力的升高而升高,表现出较好的线性度。在极不均匀电场下,1-C_(3)F_(6)/CO_(2)混合气体工频击穿电压随着充气压力的升高而缓慢升高,逐渐趋于饱和。文中的试验结果可以为电力产品设计提供参考和依据。
