为了探究针-板电极电场参数对雾化特性微量润滑磨削性能的影响,通过调节电压幅值和电极间距进行微量润滑平面磨削实验,根据所得雾化锥角、雾滴粒径算术平均值、磨削力及表面粗糙度Ra值进行机理分析。实验结果表明静电雾化微量润滑在高...为了探究针-板电极电场参数对雾化特性微量润滑磨削性能的影响,通过调节电压幅值和电极间距进行微量润滑平面磨削实验,根据所得雾化锥角、雾滴粒径算术平均值、磨削力及表面粗糙度Ra值进行机理分析。实验结果表明静电雾化微量润滑在高压静电场的参与下,液滴荷电后会发生二次甚至多次雾化。随着电压幅值的升高,雾化锥角增大,雾滴的平均粒径减小并扩散均匀,同时润滑液的润滑性能也有所提高。在电压幅值一定,电极间距为160 mm时,获得最优的润滑性能;在电极间距一定,电压幅值为50 k V时,相比于无静电微量润滑,比切向磨削力Ft'、比法向磨削力Fn'及表面粗糙度R_a值,分别减小25.01%、15.08%、22.18%,获得最优的润滑性能。展开更多
高频超声换能器已成为现代医学诊断和治疗的有力工具.目前,大多数超声换能器使用压电陶瓷进行机电耦合,在高频(>20 MHz)下会发生周期性的电声转换,因此对材料可靠性要求较高.本文提出了一种结构调控策略,以提高铌酸钾钠(KNN)基无铅...高频超声换能器已成为现代医学诊断和治疗的有力工具.目前,大多数超声换能器使用压电陶瓷进行机电耦合,在高频(>20 MHz)下会发生周期性的电声转换,因此对材料可靠性要求较高.本文提出了一种结构调控策略,以提高铌酸钾钠(KNN)基无铅陶瓷的压电性与可靠性,并用于高频超声成像.该KNN基陶瓷具有增强的压电性(d33~550±20 pC N^(-1))及抗疲劳特性,同时针对其良好性能,我们从涉及宏观到微观的多项共存、完好微观结构与灵活畴翻转的多维度协同效应阐述其机理.该多维度协同效应抑制了疲劳过程中性能恶化裂纹的出现及空间电荷的聚集,从而减少了畴壁的钉扎,增强了抗疲劳性.此外,基于该高性能压电陶瓷制备的超声换能器具有高可靠性及温度稳定性(从室温到80℃,频带宽度几乎不变).我们利用该超声换能器扫描罗非鱼眼球结构测试了器件成像效果.相信通过结构策略实现性能提升的新方法可以促进KNN基超声器件在生物医学方面的应用.展开更多
With the integration of ultrafast reflectivity and polarimetry probes,we observed carrier relaxation and spin dynamics induced by ultrafast laser excitation of Ni(111)single crystals.The carrier relaxation time within...With the integration of ultrafast reflectivity and polarimetry probes,we observed carrier relaxation and spin dynamics induced by ultrafast laser excitation of Ni(111)single crystals.The carrier relaxation time within the linear excitation range reveals that electron-phonon coupling and dissipation of photon energy into the bulk of the crystal take tens of picoseconds.On the other hand,the observed spin dynamics indicate a longer time of about 120 ps.To further understand how the lattice degree of freedom is coupled with these dynamics may require the integration of an ultrafast diffraction probe.展开更多
基金supported by the National Natural Science Foundation of China (22234005 and 21974070)the Natural Science Foundation of Jiangsu Province (BK20222015)the Young Academic Leaders of the Qing Lan Project of Jiangsu Province (SUJIAOSHIHAN[2022]No.29)。
文摘为了探究针-板电极电场参数对雾化特性微量润滑磨削性能的影响,通过调节电压幅值和电极间距进行微量润滑平面磨削实验,根据所得雾化锥角、雾滴粒径算术平均值、磨削力及表面粗糙度Ra值进行机理分析。实验结果表明静电雾化微量润滑在高压静电场的参与下,液滴荷电后会发生二次甚至多次雾化。随着电压幅值的升高,雾化锥角增大,雾滴的平均粒径减小并扩散均匀,同时润滑液的润滑性能也有所提高。在电压幅值一定,电极间距为160 mm时,获得最优的润滑性能;在电极间距一定,电压幅值为50 k V时,相比于无静电微量润滑,比切向磨削力Ft'、比法向磨削力Fn'及表面粗糙度R_a值,分别减小25.01%、15.08%、22.18%,获得最优的润滑性能。
基金supported by the National Natural Science Foundation of China(NSFC 52202144,52061130216 and 52032007)the Key-Area Research and Development Program of Guangdong Province(2020B0109380001)+2 种基金the Central Funds Guiding the Local Science and Technology Development of Sichuan Province(2021ZYD0022)the Fundamental Research Funds for the Central Universities,Sichuan University(YJ2021153)the Newton Advanced Fellowship award(NAFR1201126)from the Royal Society。
文摘高频超声换能器已成为现代医学诊断和治疗的有力工具.目前,大多数超声换能器使用压电陶瓷进行机电耦合,在高频(>20 MHz)下会发生周期性的电声转换,因此对材料可靠性要求较高.本文提出了一种结构调控策略,以提高铌酸钾钠(KNN)基无铅陶瓷的压电性与可靠性,并用于高频超声成像.该KNN基陶瓷具有增强的压电性(d33~550±20 pC N^(-1))及抗疲劳特性,同时针对其良好性能,我们从涉及宏观到微观的多项共存、完好微观结构与灵活畴翻转的多维度协同效应阐述其机理.该多维度协同效应抑制了疲劳过程中性能恶化裂纹的出现及空间电荷的聚集,从而减少了畴壁的钉扎,增强了抗疲劳性.此外,基于该高性能压电陶瓷制备的超声换能器具有高可靠性及温度稳定性(从室温到80℃,频带宽度几乎不变).我们利用该超声换能器扫描罗非鱼眼球结构测试了器件成像效果.相信通过结构策略实现性能提升的新方法可以促进KNN基超声器件在生物医学方面的应用.
基金Project supported by the National Key R&D Program of China (Grant Nos. 2022YFA1604402 and 2022YFA1604403)the National Natural Science Foundation of China (NSFC) (Grant No. 11721404)+3 种基金the Shanghai Rising-Star Program (Grant No. 21QA1406100)the Technology Innovation Action Plan of the Science and Technology Commission of Shanghai Municipality (Grant No. 20JC1416000)support by the Air Force Office of Scientific Research (AFOSR) (Grant No. FA9550-20-10139)the Texas A&M Engineering Experimental Station (TEES)
文摘With the integration of ultrafast reflectivity and polarimetry probes,we observed carrier relaxation and spin dynamics induced by ultrafast laser excitation of Ni(111)single crystals.The carrier relaxation time within the linear excitation range reveals that electron-phonon coupling and dissipation of photon energy into the bulk of the crystal take tens of picoseconds.On the other hand,the observed spin dynamics indicate a longer time of about 120 ps.To further understand how the lattice degree of freedom is coupled with these dynamics may require the integration of an ultrafast diffraction probe.
