Experimental analysis of the dynamical response of energy harvesting devices based on bistable laminated plates

The use of bistable laminates is a potential approach to realize broadband piezoelectric based energy harvesting systems. In this paper the dynamic response of a piezoelectric material attached to a bistable laminate plate is examined based on the experimental generated voltage time series. The system was subjected to harmonic excitations and exhibited single-well and snap-through vibrations of both periodic and chaotic character. To identify the dynamics of the system response we examined the frequency spectrum, bifurcation diagrams, phase portraits, and the 0–1 test

Self-aggregation phenomenon and stable flow conditions in a two-phase flow through a minichannel

cited By 6International audienceBy increasing a water flow rate of the two-phase (air-water) flow through a minichannel, both the partitioning of air slugs into air bubbles of different sizes and small air bubbles aggregation into larger air bubbles were identified. These phenomena were studied in detail by using the corresponding sequences of light transmission time series recorded with a laser-phototransistor sensor. To distinguish any instabilities in air slugs along with their break-ups and aggregations, the recurrence plots and recurrence quantification analysis were applied

Nonlinear vibration of semitrailer suspension: wavelet and multiscale entropy-based approaches

cited By 1International audienceWe examine the dynamical response of a semitrailer suspension to a real road profile under two different loads. The trailer is a low loader for transporting heavy and large loads, the configuration of which can be adjusted as desired. Experiments are performed on both unladen and 57-ton laden trailers. The acceleration of unsprung and sprung parts of the vehicle is measured. The obtained acceleration time series are then analyzed using the Fourier and wavelet transforms as well as the multiscale entropy approach. The data analysis results reveal transmission of suspension vibration and complexity of vehicle vertical acceleration as a response to the road profile. © 2015, The Author(s)

Validation of a modified 0-1 test for chaos identification in Duffing-Van der Pol oscillator

The reliability of the 0-1 test for chaos identification may be influenced by the modalities of sampling with respect to the time scales inherent in the system under consideration. In a previous work, the Authors proposed a modified version of the test based on the consideration of the time series of the local maxima of the basic trajectories. In this work, the effectiveness of the modified method is further validated by analyzing typical periodic, quasiperiodic and chaotic oscillations in the well-known Duffing-Van der Pol oscillator. The results show that transitions from regular to chaotic motion can be easily detected and that the proposed method leads to the correct results that are confirmed by standard methods like the usual 0-1 test based on Poincare ́ e points and also by the topology of corresponding Poincar ́ e maps and phase portrait

Discovery of a second family of bismuth-oxide-based superconductors

The superconducting oxide BaPb(1-x)Bi(x)O3, discovered in 1975 (ref. 1), is an exotic system having an unusually high transition temperature (T(c)) of ~12K, despite a relatively low density of states at the Fermi level. The subsequent prediction that doping the electronically inactive barium donor sites, instead of the bismuth sites, might induce superconductivity with a higher T(c) led to the discovery in 1988 of superconductivity in the Ba(1-x)K(x)BiO3 system (T(c) ~30 K for x = 0.4). But it remains an open question why many of the superconducting properties of these materials are similar to those of the well-known copper oxide superconductors, despite their pronounced structural differences: the former have a three-dimensional bismuth-oxygen framework, whereas the structures of the latter are predominantly two-dimensional, consisting of copper-oxygen planes. Understanding of the copper oxide superconductors has gained immensely from the study of many different superconducting systems, and so it might be expected that the identification of bismuth oxide superconductors beyond the substituted BaBiO3 compounds will prove to be similarly fruitful. Here we report the synthesis of a second family of superconducting bismuth oxides, based on SrBiO3. We show that partial substitution of potassium or rubidium for strontium induces superconductivity with: T(c) values of ~12 K for Sr(1-x)K(x)BiO3 (x= 0.45-0.6) and ~13K for Sr(1-x)Rb(x)BiO3 (x = 0.5)