It is first shown that the observational light curve data of R Scuti, a star of the RV Tau type, is not multi-periodic, and that it cannot have been generated by a linear stochastic (AR) process. By default, the signal must be a manifestation of deterministic chaos. We use a novel nonlinear time-series analysis, the global flow reconstruction technique, to probe the properties of the irregular pulsation cycles. We show in particular that the chaotic dynamics of this star's complicated lightcurve is captured by a simple 4D polynomial map or flow (4 first order ODEs). Importantly also, the method allows us to quantify an irregular signal which has the potential benefit for extracting novel stellar constraints from an irregular light-curve. Finally, from the low dimensionality 4 of the flow we can infer a simple physical picture of the pulsations, and arguments are presented that the pulsations of R Sct are the result of the nonlinear interaction of two vibrational normal modes of the star.
Use of bicycles on a large scale, encouraged in the context to develop an eco-friendly environment, is facing today a range of barriers. One of these barriers identified by researchers and governments is observed to include ‘road safety’. Hence, it is necessary to set up a protection system for bicyclists especially for the cephalic segment. Currently only few studies are available concerning the head impact loading in case of real accidents. Therefore, the objective of this work is to improve the knowledge of bicyclist head trauma by following a methodology to reconstruct real-world accidents. A step is to identify the initial condition of head impact in case of real accidents. Head impact velocity and head impact area are extracted and implemented in the last generation of head injury prediction tool to simulate the head trauma by impacting directly the Strasbourg University Finite Element Head Model (SUFEHM) on the vehicle structures. The present study can be divided into three activities, i.e. obtain real bicyclist accidents’ data issued from in-depth accident investigation databases, reconstruct cyclist body kinematics to obtain the initial conditions of the head just before the impact, and simulate head impact to evaluate the head loading during impact and the injury risk. A total of 24 bicyclists’ accident cases with head injuries have been selected from both French and German accident databases. For each accident case, body kinematics has been simulated using Madymo® software. Two human multi-body models were used: 8 accident cases have been reconstructed by IFSTTAR using its owned developed human model and 18 accident cases have been reconstructed by Unistra using the human pedestrian TNO model. The results show that head is impacted more often on top parietal zone, and the mean impact velocity is 6.8 ± 2.7 m/s with 5.5 ± 3.0 m/s and 3.4 ± 2.1 m/s for normal and tangential components, respectively. Among these real accidents, 19 cases were selected for finite element computations by coupling the human head model and a windscreen model whose properties were extracted from literature. All reconstructed head impact gave results in accordance with the damage actually incurred to the victims
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