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Lenti L.,French Institute of Science and Technology for Transport | Martino S.,University of Rome La Sapienza
Engineering Geology | Year: 2012

The interaction of seismic waves with slopes is a major factor influencing landslide movements that involve slope stability, local site seismic amplification and topographic effects affecting ground motion. The results of a numerical study of landslide movements induced by the interaction of seismic waves with step-like slopes are presented here. To investigate this input-slope interaction, a dynamic analysis was performed using the finite difference stress-strain numerical code FLAC 6.0 under visco-plastic conditions. The dynamic signals were selected to be representative of different peak ground accelerations (PGAs), Arias intensities and frequency contents, and they were used in a parametric study of different step-like slopes with different geometrical configurations in terms of dip, height and thickness of geological strata. The derived outputs were processed for a seismic amplification analysis and to evaluate the induced stress-strain effects in terms of progressive failure and resulting displacements. The obtained results: i) describe a fundamental role of topography in amplifying or de-amplifying the seismic ground motion; ii) demonstrate that the progressive failure of unsheared slopes influences the seismic amplification; iii) show that the strain effects on unsheared slopes, in terms of progressive failure, are more intense with increasing Arias intensity and slope dip; iv) prove that amplification or de-amplification processes can justify the values of displacements involving pre-existing landslide masses, which are significantly different with respect to those expected on the basis of sliding block approaches (i.e., Newmark's and flexible sliding block methods); v) highlight that, in the geological setting considered here, the seismically induced displacements arising from the reactivation of pre-existing landslide masses can be significantly underestimated by sliding block approaches in the case of low-angle slopes characterised by high K values, i.e. the ratios between the critical pseudostatic threshold (k y) of the landslide and PGAs of the applied seismic input. © 2011 Elsevier B.V. Source

Salah K.,French Institute of Science and Technology for Transport
European Transport Research Review | Year: 2014

Flight path optimization is designed for minimizing environmental impacts of aircraft around airports during approaches. The main objective of this paper is to develop a model of optimal flight paths taking into account jet noise, fuel consumption, constraints and extreme operational limits of the aircraft in approach. A two-segment approach is obtained as an optimal trajectory. Aircraft alignment on the runway axis with a slope of 3° during the last approach segment is observed and the descent rate is about 1060 ft/mn. This particularly characterizes the continuous descent approach having the potential to reduce noise emission by -4 dB and fuel consumption by -20 % to -10 % during the approach. Measurements of aircraft noise were carried out around Saint-Exupry Lyon International Airport for one year. Because of the suggested trajectory, optimized noise levels are less than the measured and INM values. Optimal trajectory consumes less than the standard trajectory; it can be integrated in the aircraft FMS and used in the autopilot system. This is one of the promising objectives of this research. © 2013 The Author(s). Source

Ghazel M.,French Institute of Science and Technology for Transport
Transportation Research Part C: Emerging Technologies | Year: 2014

ERTMS is the standard railway control-command and signaling system which aims to ensure railway interoperability throughout Europe while enhancing safety and competitiveness. ERTMS is composed of two main subsystems which include GSM-R, a radio system for enabling communication between the train and the traffic management center and ETCS, an automatic train protection system (ATP) to replace the existing national ATP systems. The ERTMS specifications are defined by means of standard documents which set out the requirements ensuring interoperability. These documents evolve regularly to give rise to successive versions. The ERTMS/ETCS standard defines different levels and operation modes according to various trackside and onboard setups and some operational conditions. Given the complexity and the high criticality of railway operation, verification and validation (V&V) are crucial tasks in railway application development. In this paper, after setting the background and the motivations, a mechanizable formalization of a subset of ERTMS/ETCS specifications relative to ETCS modes and transitions is developed. The present work aims to offer a readily available model for formal V&V. Using formal techniques to check SRS is highly recommended to tackle the complexity of the defined requirements and prevent specification errors. Model-checking technique, which is targeted here, offers exhaustive analysis of the system behavior based on its model and is highly automated, since it is supported by software tools. Based on the last available version of SRS specifications, a progressive process is undertaken to get a formal model which makes explicit the various modes characterized by their respective active functions, as well as the numerous combinations of conditions for switching between modes. The various steps guiding the translation of the SRS literal specifications into a formal model are explained. As will be shown through different examples, the obtained model is a convenient basis to check safety, interoperability and liveness properties. © 2014 Elsevier Ltd. Source

Avenas Y.,Joseph Fourier University | Dupont L.,French Institute of Science and Technology for Transport | Khatir Z.,French Institute of Science and Technology for Transport
IEEE Transactions on Power Electronics | Year: 2012

This paper proposes a synthesis of different electrical methods used to estimate the temperature of power semiconductor devices. The following measurement methods are introduced: the voltage under low current levels, the threshold voltage, the voltage under high current levels, the gate-emitter voltage, the saturation current, and the switching times. All these methods are then compared in terms of sensitivity, linearity, accuracy, genericity, calibration needs, and possibility of characterizing the thermal impedance or the temperature during the operation of the converter. The measurement of thermo-sensitive parameters of wide bandgap semiconductors is also discussed. © 2006 IEEE. Source

Vinot E.,French Institute of Science and Technology for Transport | Trigui R.,French Institute of Science and Technology for Transport
Energy Conversion and Management | Year: 2013

Energy storage systems are a key point in the design and development of electric and hybrid vehicles. In order to reduce the battery size and its current stress, a hybrid storage system, where a battery is coupled with an electrical double-layer capacitor (EDLC) is considered in this paper. The energy management of such a configuration is not obvious and the optimal operation concerning the energy consumption and battery RMS current has to be identified. Most of the past work on the optimal energy management of HEVs only considered one additional power source. In this paper, the control of a hybrid vehicle with a hybrid storage system (HSS), where two additional power sources are used, is presented. Applying the Pontryagin's minimum principle, an optimal energy management strategy is found and compared to a rule-based parameterized control strategy. Simulation results are shown and discussed. Applied on a small compact car, optimal and ruled-based methods show that gains of fuel consumption and/or a battery RMS current higher than 15% may be obtained. The paper also proves that a well tuned rule-based algorithm presents rather good performances when compared to the optimal strategy and remains relevant for different driving cycles. This rule-based algorithm may easily be implemented in a vehicle prototype or in an HIL test bench. © 2013 Elsevier Ltd. All rights reserved. Source

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