Monitoring minuscule mechanical signals,both in magnitude and direction,is imperative in many application scenarios,e.g.,structural health monitoring and robotic sensing systems.However,the piezoelectric sensor strugg...Monitoring minuscule mechanical signals,both in magnitude and direction,is imperative in many application scenarios,e.g.,structural health monitoring and robotic sensing systems.However,the piezoelectric sensor struggles to satisfy the requirements for directional recognition due to the limited piezoelectric coefficient matrix,and achieving sensitivity for detecting micrometer-scale deformations is also challenging.Herein,we develop a vector sensor composed of lead zirconate titanate-electronic grade glass fiber composite filaments with oriented arrangement,capable of detecting minute anisotropic deformations.The as-prepared vector sensor can identify the deformation directions even when subjected to an unprecedented nominal strain of 0.06%,thereby enabling its utility in accurately discerning the 5μm-height wrinkles in thin films and in monitoring human pulse waves.The ultra-high sensitivity is attributed to the formation of porous ferroelectret and the efficient load transfer efficiency of continuous lead zirconate titanate phase.Additionally,when integrated with machine learning techniques,the sensor’s capability to recognize multi-signals enables it to differentiate between 10 types of fine textures with 100%accuracy.The structural design in piezoelectric devices enables a more comprehensive perception of mechanical stimuli,offering a novel perspective for enhancing recognition accuracy.展开更多
Fluidelastic instability is destructive in tube bundles subjected to cross flow.Flow channel model proposed by Leaver and Weaver is well used for modeling this problem.However,as the tube motion is supposed to be harm...Fluidelastic instability is destructive in tube bundles subjected to cross flow.Flow channel model proposed by Leaver and Weaver is well used for modeling this problem.However,as the tube motion is supposed to be harmonic,it may not simulate the general dynamic behaviors of tubes.To improve this,a model with arbitrary tube motion is proposed by Hassan and Hayder.While,due to involving in the time delay term,the stability problem cannot be solved by the eigenvalue scheme,and time domain responses of the tube have to be obtained to assess the instability threshold.To overcome this weakness,a new approach based on semi-discretizing method(SDM)is proposed in this study to make the instability threshold be predicted by eigenvalues directly.The motion equation of tube is built with considering the arbitrary tube motion and the time delay between fluid flow and tube vibration.A time delay integral term is derived and the SDM is employed to construct a transfer matrix,which transforms the infinite dimensional eigenvalue problem into a finite one.Hence the stability problem become solvable accordingly.With the proposed method,the instability threshold of a typical square tube array model is predicted,and the influences of system parameters on stability are also discussed.With comparing with prior works,it shows significant efficiency improvement in prediction of the instability threshold of tube bundles.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2022YFA1205300 and No.2022YFA1205304)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(SL2022ZD103).
文摘Monitoring minuscule mechanical signals,both in magnitude and direction,is imperative in many application scenarios,e.g.,structural health monitoring and robotic sensing systems.However,the piezoelectric sensor struggles to satisfy the requirements for directional recognition due to the limited piezoelectric coefficient matrix,and achieving sensitivity for detecting micrometer-scale deformations is also challenging.Herein,we develop a vector sensor composed of lead zirconate titanate-electronic grade glass fiber composite filaments with oriented arrangement,capable of detecting minute anisotropic deformations.The as-prepared vector sensor can identify the deformation directions even when subjected to an unprecedented nominal strain of 0.06%,thereby enabling its utility in accurately discerning the 5μm-height wrinkles in thin films and in monitoring human pulse waves.The ultra-high sensitivity is attributed to the formation of porous ferroelectret and the efficient load transfer efficiency of continuous lead zirconate titanate phase.Additionally,when integrated with machine learning techniques,the sensor’s capability to recognize multi-signals enables it to differentiate between 10 types of fine textures with 100%accuracy.The structural design in piezoelectric devices enables a more comprehensive perception of mechanical stimuli,offering a novel perspective for enhancing recognition accuracy.
基金The support from the National Natural Science Foundation of China(No.11672179)is greatly acknowledged.
文摘Fluidelastic instability is destructive in tube bundles subjected to cross flow.Flow channel model proposed by Leaver and Weaver is well used for modeling this problem.However,as the tube motion is supposed to be harmonic,it may not simulate the general dynamic behaviors of tubes.To improve this,a model with arbitrary tube motion is proposed by Hassan and Hayder.While,due to involving in the time delay term,the stability problem cannot be solved by the eigenvalue scheme,and time domain responses of the tube have to be obtained to assess the instability threshold.To overcome this weakness,a new approach based on semi-discretizing method(SDM)is proposed in this study to make the instability threshold be predicted by eigenvalues directly.The motion equation of tube is built with considering the arbitrary tube motion and the time delay between fluid flow and tube vibration.A time delay integral term is derived and the SDM is employed to construct a transfer matrix,which transforms the infinite dimensional eigenvalue problem into a finite one.Hence the stability problem become solvable accordingly.With the proposed method,the instability threshold of a typical square tube array model is predicted,and the influences of system parameters on stability are also discussed.With comparing with prior works,it shows significant efficiency improvement in prediction of the instability threshold of tube bundles.
