Revealing the deterministic components in active avalanche-like dynamics

Soft Matter ◽  
2021 ◽  
Author(s):  
Ishant Tiwari ◽  
Swanith Upadhye ◽  
V. S. Akella ◽  
P. Parmananda
Keyword(s):  
Natural Frequency ◽  
External Forcing ◽  
Resonant Response ◽  
Deterministic Component ◽  
System P ◽  
Deterministic Components

An ensemble of autonomous camphor discs exhibits avalanche-like dynamics with a characteristic/natural frequency. Furthermore, the dynamics show a resonant response to external forcing indicating the presence of a deterministic component in the system.

Dual resonance in vortex-induced vibrations at subcritical and supercritical Reynolds numbers

2010 ◽  
Vol 643 ◽  
pp. 395-424 ◽  
Author(s):  
J. M. DAHL ◽  
F. S. HOVER ◽  
M. S. TRIANTAFYLLOU ◽  
O. H. OAKLEY
Keyword(s):  
Reynolds Number ◽  
Natural Frequency ◽  
Frequency Ratio ◽  
Reynolds Numbers ◽  
Large Reynolds Number ◽  
Resonant Response ◽  
Third Harmonic ◽  
Vortex Induced Vibrations ◽  
Dual Resonance ◽  
Harmonic Components

An experimental study is performed on the vortex induced vibrations of a rigid flexibly mounted circular cylinder placed in a crossflow. The cylinder is allowed to oscillate in combined crossflow and in-line motions, and the ratio of the nominal in-line and transverse natural frequencies is varied systematically. Experiments were conducted on a smooth cylinder at subcritical Reynolds numbers between 15 000 and 60 000 and on a roughened cylinder at supercritical Reynolds numbers between 320 000 and 710 000, with a surface roughness equal to 0.23 % of the cylinder diameter. Strong qualitative and quantitative similarities between the subcritical and supercritical experiments are found, especially when the in-line natural frequency is close to twice the value of the crossflow natural frequency. In both Reynolds number regimes, the test cylinder may exhibit a ‘dual-resonant’ response, resulting in resonant crossflow motion at a frequency fv, near the Strouhal frequency, and resonant in-line motion at 2 fv. This dual resonance is shown to occur over a relatively wide frequency region around the Strouhal frequency, accompanied by stable, highly repeatable figure-eight cylinder orbits, as well as large third-harmonic components of the lift force. Under dual-resonance conditions, both the subcritical and the supercritical response is shown to collapse into a narrow parametric region in which the effective natural-frequency ratio is near the value 2, regardless of the nominal natural-frequency ratio. Some differences are noted in the magnitudes of forces and the cylinder response between the two different Reynolds number regimes, but the dual-resonant response and the resulting force trends are preserved despite the large Reynolds number difference.

Singing Propellers—Solutions and Case Histories

2008 ◽  
Vol 45 (04) ◽  
pp. 221-227
Author(s):  
Raymond Fischer
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Vortex Shedding ◽  
Resonant Response ◽  
Case Histories ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency ◽  
Propeller Blades ◽  
Marine Vessels

This paper examines the hydroacoustic processes involved with "singing propellers" aboard marine vessels. Methods are presented to determine the potential for a resonant response of a propeller to a vortex shedding excitation—a phenomenon known as "singing." Methods are provided to determine the likely shedding frequency and structural natural frequency for propeller blades. Diagnostics procedures to determine the presence of singing are explored. Measured and theoretical differences between the blade's natural frequency response in air and in-water are explored. Treatments are identified to change the vortex shedding frequency or to de-tune the structure. Case histories are detailed showing the potential magnitude of the problem and effective solutions.

A dynamic model of laminated material extrusion additive manufacturing plate with the property of orthogonal anisotropy

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Shijie Jiang ◽  
Mingyu Sun ◽  
Yang Zhan ◽  
Hui Li ◽  
Wei Sun
Keyword(s):  
Sensitivity Analysis ◽  
Additive Manufacturing ◽  
Dynamic Model ◽  
Natural Frequency ◽  
Dynamic Behavior ◽  
Theoretical Basis ◽  
Resonant Response ◽  
Content Type ◽  
Set Up ◽  
Orthogonal Anisotropy

Purpose The purpose of this study is to set up a dynamic model of material extrusion (ME) additive manufacturing plates for the prediction of their dynamic behavior (i.e. dynamic inherent characteristic, resonant response and damping) and also carry out its experimental validation and sensitivity analysis. Design/methodology/approach Based on the classical laminated plate theory, a dynamic model is established using the orthogonal polynomials method, taking into account the effect of lamination and orthogonal anisotropy. The dynamic inherent characteristics of the ME plate are worked out by Ritz method. The frequency-domain dynamic equations are then derived to solve the plates’ resonant responses, with which the damping ratio is figured out according to the half-power bandwidth method. Subsequently, a series of experimental tests are performed on the ME samples to obtain the measured data. Findings It is shown that the predictions and measurements in terms of dynamic behavior are in good agreement, validating the accuracy of the developed model. In addition, sensitivity analysis shows that increasing the elastic modulus or Poisson’s ratio will increase the corresponding natural frequency of the ME plate but decrease the resonant response. When the density is increased, both the natural frequency and resonant response will be decreased. Research limitations/implications Future research can be focused on using the proposed model to investigate the effect of processing parameters on the ME parts’ dynamic behavior. Practical implications This study shows theoretical basis and technical insight into improving the forming quality and reliability of the ME parts. Originality/value A novel reliable dynamic model is set up to provide theoretical basis and principle to reveal the physical phenomena and mechanism of ME parts.

Comparison of TEM and STM observations of small silver clusters on different carbon supports

1990 ◽  
Vol 48 (4) ◽  
pp. 264-265
Author(s):  
Bernd Tesche ◽  
Tobias Schilling
Keyword(s):  
Vibration Isolation ◽  
Pyrolytic Graphite ◽  
Carbon Film ◽  
Silver Clusters ◽  
Carbon Supports ◽  
Stacking Order ◽  
System P ◽  
High Resolution Tem ◽  
High Degree ◽  
Degree Of Order

The objective of our work is to determine:a) whether both of the imaging methods (TEM, STM) yield comparable data andb) which method is better suited for a reliable structure analysis of microclusters smaller than 1.5 nm, where a deviation of the bulk structure is expected.The silver was evaporated in a bell-jar system (p 10−5 pa) and deposited onto a 6 nm thick amorphous carbon film and a freshly cleaved highly oriented pyrolytic graphite (HOPG).The average deposited Ag thickness is 0.1 nm, controlled by a quartz crystal microbalance at a deposition rate of 0.02 nm/sec. The high resolution TEM investigations (100 kV) were executed by a hollow-cone illumination (HCI). For the STM investigations a commercial STM was used. With special vibration isolation we achieved a resolution of 0.06 nm (inserted diffraction image in Fig. 1c). The carbon film shows the remarkable reduction in noise by using HCI (Fig. 1a). The HOPG substrate (Fig. 1b), cleaved in sheets thinner than 30 nm for the TEM investigations, shows the typical arrangement of a nearly perfect stacking order and varying degrees of rotational disorder (i.e. artificial single crystals). The STM image (Fig. 1c) demonstrates the high degree of order in HOPG with atomic resolution.

Conclusion: What is Speculative Empiricism?

2018 ◽  
Author(s):  
Didier Debaise
Keyword(s):  
Social Groups ◽  
Speculative Philosophy ◽  
System P ◽  
History Of ◽  
Selection Of

Process and Reality ends with a warning: ‘[t]he chief danger to philosophy is narrowness in the selection of evidence’ (PR, 337). Although this danger of narrowness might emerge from the ‘idiosyncrasies and timidities of particular authors, of particular social groups, of particular schools of thought, of particular epochs in the history of civilization’ (PR, 337), we should not be mistaken: it occurs within philosophy, in its activity, its method. And the fact that this issue arises at the end of Process and Reality reveals the ambition that has accompanied its composition: Whitehead has resisted this danger through the form and ambition of his speculative construction. The temptation of a narrowness in selection attempts to expel speculative philosophy at the same time as it haunts each part of its system.

Influence of the distribution of the shear walls on the seismic response of the buildings

2020 ◽  
Vol 15 (1) ◽  
pp. 37-44
Author(s):  
El Mehdi Echebba ◽  
Hasnae Boubel ◽  
Oumnia Elmrabet ◽  
Mohamed Rougui
Keyword(s):  
Structural Analysis ◽  
Seismic Response ◽  
Natural Frequency ◽  
Structural Design ◽  
Structural Response ◽  
Shear Walls ◽  
Structural Elements ◽  
Analysis Software ◽  
Ansys Apdl ◽  
The Impact

Abstract In this paper, an evaluation was tried for the impact of structural design on structural response. Several situations are foreseen as the possibilities of changing the distribution of the structural elements (sails, columns, etc.), the width of the structure and the number of floors indicates the adapted type of bracing for a given structure by referring only to its Geometric dimensions. This was done by studying the effect of the technical design of the building on the natural frequency of the structure with the study of the influence of the distribution of the structural elements on the seismic response of the building, taking into account of the requirements of the Moroccan earthquake regulations 2000/2011 and using the ANSYS APDL and Robot Structural Analysis software.

Pedestrian Oriented Vehicular Collision Avoidance Support System: P-VCASS

2010 ◽  
Vol E93-A (4) ◽  
pp. 679-688 ◽  
Author(s):  
Tomotaka WADA ◽  
Yuki NAKANISHI ◽  
Ryohta YAMAGUCHI ◽  
Kazushi FUJIMOTO ◽  
Hiromi OKADA
Keyword(s):  
Collision Avoidance ◽  
Support System ◽  
System P

Effect of Curved Thin-film Device on Natural Frequency of Rectangle Membrane under Uniaxial Tension

2019 ◽  
Vol 18 (0) ◽  
pp. 73-80 ◽  
Author(s):  
Masanori MATSUSHITA ◽  
Nobukatsu OKUIZUMI ◽  
Yasutaka SATOU ◽  
Osamu MORI ◽  
Takashi IWASA ◽  
...  
Keyword(s):  
Thin Film ◽  
Uniaxial Tension ◽  
Natural Frequency ◽  
Thin Film Device
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