Dynamical Stability of Cantilevered Pipe Conveying Fluid with Inerter-Based Dynamic Vibration Absorber

Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantilevered fluid-conveying pipe attached by an inerter-based dynamic vibration absorber(IDVA)is proposed and the stability of this dynamical system is explored.Based on linear governing equations of the pipe and the IDVA,the effects of damping coefficient,weight,inerter,location and spring stiffness of the IDVAon the critical flow velocities of the pipe system is examined.It is shown that the stability of the pipe may be significantly affected by the IDVA.In many cases,the stability of the cantilevered pipe can be enhanced by designing the parameter values of the IDVA.By solving nonlinear governing equations of the dynamical system,the nonlinear oscillations of the pipe with IDVA for sufficiently high flow velocity beyond the critical value are determined,showing that the oscillation amplitudes of the pipe can also be suppressed to some extent with a suitable design of the IDVA.

通过Ag阵列耦合增强少层InSe的光学响应

具有高发光性能的二维材料被认为是实现光电器件应用的极具前途的材料.其中,硒化铟(InSe)是一种具有代表性的二维材料,近些年在光电领域表现出巨大的应用潜力,因此吸引了研究者们的广泛关注.然而,InSe的光-物质相互作用极其微弱,因为其带隙激子的偏振取向是面外的,主要被面外偏振光激发而对正常入射光(面内偏振)的响应极其微弱,这大大限制了其在光电器件中的实际应用.在此,我们提出了一种方法,即通过将少层InSe转移到Ag纳米棱镜阵列上,显著提升InSe在线性和非线性体系的光学响应.结合实验分析,增强的机理主要来自于两种机制的协同作用:一方面,局域表面等离子体共振产生的局部强化电磁场垂直分布于金属表面,与面外偏振的InSe带隙激子发生高效耦合,增强了InSe的光-物质相互作用;另一方面,独特设计的弯曲结构增加了入射光在平面外的偏振分量,促使InSe面外激子对光的吸收和散射效率增强.通过进一步调整InSe的厚度,我们实现了光致发光和二次谐波信号的两个数量级的增强.因此,我们的工作为改善InSe的光学特性提供了一个有效的途径,使其在光电器件的实际应用中迈出了重要的一步.