An active metasurface for real-time multifunctional elastic wave control (Conference Presentation)

2018 ◽  
Author(s):  
Yangyang Chen ◽  
Xiaopeng Li ◽  
Guoliang Huang
Keyword(s):  
Elastic Wave ◽  
Real Time ◽  
Wave Control

scholarly journals Broadband, reconfigurable and multifunctional elastic wave control with smart metamaterials

2017 ◽  
Author(s):  
◽  
Yangyang Chen
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Real Time ◽  
Smart Materials ◽  
Extreme Values ◽  
Research Effort ◽  
Rapid Development ◽  
Active Noise Control ◽  
Elastic Metamaterials ◽  
Wave Control

Over the past two decades, an extensive research effort has been devoted to elastic metamaterials, structured artificial materials at subwavelength scales, for elastic wave manipulations in solids. Due to the extreme values of material parameters, negative and/or positive, they achieved, the applications can range from wave and/or vibration attenuations, wave guiding and imaging, enhanced sensing, to invisible cloaking. However, conventional passive metamaterials have limitations, i.e. they can only be operated in narrow frequency regions and their functions are usually locked into space or with minor tunabilities once fabricated, lacking real time reconfigurabilities. Those limitations strongly hinder them from practical usages. With the rapid development of smart materials and structures, more and more intelligent elements are being introduced into wave propagation, vibration and sound control systems. The piezoelectric shunting technique is one well known method that receives considerable attention. In this dissertation, by leveraging the circuit control concept, both analog and digital, we propose some circuit controlled active/adaptive/hybrid/programmable metamaterials and metasurfaces for unprecedent elastic wave manipulations. Analytical, numerically and experimentally approaches are combined throughout the dissertation to illustrate design concepts, characterize wave propagation properties, and valid the designs. Specifically, active elastic metamaterials with tunable stiffness in local resonators are first designed for tunable wave and/or vibration mitigations. We then extend this concept to achieve super broadband wave attenuations with frequency-dependent stiffness elements. By introducing the variable stiffness elements to the host medium, a hybrid metamaterial is developed for switched ON/OFF wave propagations and broadband negative refractions. Based on a developed approximate transformation method, an active metamaterial is designed and placed on a plate to achieve spatially varying effective mass densities for broadband elastic trajectory control. Finally, a programmable metasurface with ultrathin-thickness is demonstrated for broadband, real-time and multifunctional wavefront manipulations in a plate. The active, adaptive, hybrid, and programmable elastic metamaterials and/or metasurfaces are still in their infant stages. The examples presented in the dissertation are transformable to different length and time scales and could serve as efficient and powerful tools in exploring some unconventional wave phenomenon in solid structures, i.e. by using concepts in quantum mechanics, where passive approaches are significantly limited. The designs could also immediately open new possibilities in elastic wave control devices including, but not limited to structural health monitoring, stealth technology, active noise control, as well as medical instrumentation and imaging.

Machine-learning based design of digital materials for elastic wave control

2021 ◽  
pp. 101372
Author(s):  
Jingyi Zhang ◽  
Yiwen Li ◽  
Tianyu Zhao ◽  
Quan Zhang ◽  
Lei Zuo ◽  
...  
Keyword(s):  
Machine Learning ◽  
Elastic Wave ◽  
Wave Control

scholarly journals Longitudinal elastic wave control by pre-deforming semi-linear materials

2017 ◽  
Vol 142 (3) ◽  
pp. 1229-1235 ◽  
Author(s):  
Dengke Guo ◽  
Yi Chen ◽  
Zheng Chang ◽  
Gengkai Hu
Keyword(s):  
Elastic Wave ◽  
Longitudinal Elastic Wave ◽  
Wave Control

scholarly journals Wave Mode Control of Cantilever Slab Structure of T-Beam Bridge with Large Aspect Ratio

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Tingting Liu ◽  
Chuanping Zhou ◽  
Zhigang Yan ◽  
Guojin Chen
Keyword(s):  
Aspect Ratio ◽  
Elastic Wave ◽  
Wave Mode ◽  
Control Force ◽  
Cantilever Plate ◽  
Large Aspect Ratio ◽  
Plate Structure ◽  
Beam Bridge ◽  
T Beam ◽  
Wave Control

The cantilever plate structure in a T-beam bridge with a large aspect ratio will cause vibration under the influence of environmental disturbance and self-stress, resulting in fatigue damage of the plate structure. Wave control based on elastic wave theory is an effective method to suppress the vibration of the cantilever plate structure in a beam bridge. Based on the classical thin plate theory and the wave control method, the active vibration control of the T-shaped cantilever plate with a large aspect ratio in the beam bridge is studied in this paper. The wave mode control strategy of structural vibration is analyzed and studied, the controller is designed, the vibration mode function of the cantilever plate is established, and the control force/sensor feedback wave control is implemented for the structure. The dynamic response of the cantilever plate before and after applying wave control force is analyzed through numerical examples. The results show that the response of the structure is intense before control, but after wave control, the structure increases damping, absorbs the energy carried by the elastic wave in the structure, weakens the sharp response, and changes the natural frequency of the structure to a certain extent.

scholarly journals Elastic Wave Control Beyond Band-Gaps: Shaping the Flow of Waves in Plates and Half-Spaces with Subwavelength Resonant Rods

2017 ◽  
Vol 3 ◽  
Author(s):  
Andrea Colombi ◽  
Richard V. Craster ◽  
Daniel Colquitt ◽  
Younes Achaoui ◽  
Sebastien Guenneau ◽  
...  
Keyword(s):  
Elastic Wave ◽  
Band Gaps ◽  
Wave Control

Some Recent Results in Quiescent Prominence Spectrometry

1979 ◽  
Vol 44 ◽  
pp. 41-47
Author(s):  
Donald A. Landman
Keyword(s):  
Real Time ◽  
Computer System ◽  
Spectral Response ◽  
Absolute Intensity ◽  
Solar Observatory ◽  
Target Size ◽  
Small Target ◽  
Signal Averaging ◽  
Quiescent Prominence

This paper describes some recent results of our quiescent prominence spectrometry program at the Mees Solar Observatory on Haleakala. The observations were made with the 25 cm coronagraph/coudé spectrograph system using a silicon vidicon detector. This detector consists of 500 contiguous channels covering approximately 6 or 80 Å, depending on the grating used. The instrument is interfaced to the Observatory’s PDP 11/45 computer system, and has the important advantages of wide spectral response, linearity and signal-averaging with real-time display. Its principal drawback is the relatively small target size. For the present work, the aperture was about 3″ × 5″. Absolute intensity calibrations were made by measuring quiet regions near sun center.

Sign in / Sign up

Export Citation Format

Share Document