Low frequency collective vibration modes of the CO2 monolayer adsorbed on the NaCl(100) surface: interpretation of dispersion curves and mode polarizations

1995 ◽  
Vol 322 (1-3) ◽  
pp. 381-390 ◽  
Author(s):  
S. Picaud ◽  
P.N.M. Hoang ◽  
C. Girardet
2021 ◽  
Vol 88 (5) ◽  
Author(s):  
Mingkai Zhang ◽  
Jinkyu Yang ◽  
Rui Zhu

Abstract In this research, we aim to combine origami units with vibration-filtering metastructures. By employing the bistable origami structure as resonant unit cells, we propose metastructures with low-frequency vibration isolation ability. The geometrical nonlinearity of the origami building block is harnessed for the adjustable stiffness of the metastructure’s resonant unit. The quantitative relationship between the overall stiffness and geometric parameter of the origami unit is revealed through the potential energy analysis. Both static and dynamic experiments are conducted on the bistable origami cell and the constructed beam-like metastructure to verify the adjustable stiffness and the tunable vibration isolation zone, respectively. Finally, a two-dimensional (2D) plate-like metastructure is designed and numerically studied for the control of different vibration modes. The proposed origami-based metastructures can be potentially useful in various engineering applications where structures with vibration isolation abilities are appreciated.


Author(s):  
Costin D. Untaroiu ◽  
Alexandrina Untaroiu ◽  
Matthew Wagner ◽  
Paul E. Allaire

To reduce the vibration levels in a complex structure, the designer often needs to know how the vibrations in one part of a structure are transmitted to other parts at each interface of the connected components. A lumped-mass method and component mode synthesis is used to evaluate the power flow for vibrations in low-frequency range. The model mass and stiffness matrices are portioned into substructures separated by the interfaces whose power flow should be evaluated. The vibration modes of the substructure are divided into constrained and fixed interface modes corresponding to the interface and interior degree of freedoms, respectively. The effective interface mass criterion is used to rank the most dynamic important modes at each interface. The most important modes are preserved in a reduced model for computing the power flow. A numerical example of a linear system is used to illustrate the application of the new technique.


2018 ◽  
Vol 60 (5) ◽  
pp. 1029
Author(s):  
А.В. Савин

AbstractUsing the COMPASS force field, natural linear vibrations of graphane (graphene hydrogenated on both sides) nanoribbons are simulated. The frequency spectrum of a graphane sheet consists of three continuous intervals (low-frequency, mid-frequency, and narrow high-frequency) and two gaps between them. The construction of dispersion curves for nanoribbons with a zigzag and chair structure of the edges show that the frequencies of edge vibrations (edge phonons) can be present in the gaps of the frequency spectrum. In the first type of nanoribbons, two dispersion curves are in the low-frequency gap of the spectrum and four dispersion curves in the second gap. These curves correspond to phonons moving only along the nanoribbon edges (the mean depth of their penetration toward the nanoribbon center does not exceed 0.15 nm).


2008 ◽  
Vol 123 (5) ◽  
pp. 3599-3599 ◽  
Author(s):  
Dominique Decultot ◽  
Romain Liétard ◽  
Farid Chati ◽  
Gerard Maze ◽  
Aleksander Klauson

Author(s):  
Fadi Dohnal ◽  
Aleš Tondl

Introducing time-periodicity in system parameters may lead, in general, to a dangerous and well-known parametric resonance. In contrast to such a resonance, a properly tuned time-periodicity is capable of transferring energy between vibration modes. Time-periodicity in combination with system damping is capable of efficiently extracting vibrational energy from the system and of amplifying the existing damping affecting transient vibrations. Operating the system at such a specific time-periodicity, the system is tuned at a parametric anti-resonance. The basic principle of this concept has been studied theoretically and was proven experimentally. The physical interpretation of this concept was proposed in “Damping by Parametric Stiffness Excitation: Resonance and Anti-Resonance”, Journal of Vibration and Control, 2008, for a multiple degrees of freedom system. The present contribution highlights those findings on a multiple degrees of freedom system. It is illustrated that a parametric anti-resonance is connected to inducing an energy transfer between two of the many vibration modes of the underlying system with constant coefficients. The induced energy transfer can be utilized to transfer the vibration energy from low frequency to high frequency or vice versa or, in case of system damping, to a more efficient dissipation of vibrational energy. The achievable energy dissipation is most significant if an energy transfer is induced between a lightly damped mode and a strongly damped mode.


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