Akka Technologies

Akka, France

Akka Technologies

Akka, France

Time filter

Source Type

Jorda L.,Aix - Marseille University | Gaskell R.,Planetary Science Institute | Capanna C.,Aix - Marseille University | Hviid S.,Planetary Science Institute | And 47 more authors.
Icarus | Year: 2016

The Rosetta spacecraft reached Comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) in August 2014 at an heliocentric distance of 3.6 a.u. and was then put in orbit around its nucleus to perform detailed observations. Among the collected data are the images acquired by the OSIRIS instrument up to the perihelion passage of the comet in August 2015, which allowed us to map the entire nucleus surface at high-resolution in the visible. Stereophotoclinometry methods have been used to reconstruct a global high-resolution shape model and to monitor its rotational parameters using data collected up to perihelion.The nucleus has a conspicuous bilobate shape with overall dimensions along its principal axes of (4.34 ± 0.02) × (2.60 ± 0.02) × (2.12 ± 0.06) km. The best-fit ellipsoid dimensions of the individual lobes along their principal axes of inertia are found to be 4.10 × 3.52 × 1.63 km and 2.50 × 2.14 × 1.64 km. Their volume amounts to 66% and 27% of the total volume of the nucleus. The two lobes are connected by a "neck" whose volume has been estimated to represent ~7% of the total volume of the comet. Combining the derived volume of 18.8 ± 0.3 km3 with the mass of 9.982 ± 0.003 × 1012 kg determined by the Rosetta/RSI experiment, we obtained a bulk density of the nucleus of 532±7kgm-3. Together with the companion value of 535±35kgm-3 deduced from the stereophotogrammetry shape model of the nucleus (Preusker et al. [2015] Astron. Astrophys. 583, A33), these constitute the first reliable and most accurate determination of the density of a cometary nucleus to date. The calculated porosity is quite large, ranging approximately from 70% to 75% depending upon the assumed density of the dust grains and the dust-to-ice mass ratio. The nature of the porosity, either micro or macro or both, remains unconstrained. The coordinates of the center of gravity are not compatible with a uniform nucleus density. The direction of the offset between the center of gravity and the center of figure suggests that the big lobe has a slightly higher bulk density compared to the small one. the center of mass position cannot be explained by different, but homogenous densities in the two lobes.The initial rotational period of 12.4041 ± 0.0001 h of the nucleus persisted until October 2014. It then slightly increased to a maximum of 12.4304 h reached on 19 May 2015 and finally dropped to 12.305 h just before perihelion on August 10, 2015. A periodogram analysis of the (RA, Dec) direction of the Z-axis of the comet obtained in parallel with the shape reconstruction exhibits a highly significant minima at 11.5 ± 0.5 day clearly indicating an excited rotational state with an amplitude of 0.15 ± 0.03°. © 2016 Elsevier Inc.


Rahni A.,AKKA Technologies | Grolleau E.,University of Poitiers | Richard M.,University of Poitiers | Richard P.,University of Poitiers
Real-Time Systems | Year: 2012

The objective of this paper is two-fold: give a survey of response time analysis (RTA), and contribute to schedulability analysis for the real-time transaction model. The RTA is studied under fixed priority policies (FPP), while schedulability analysis assumes an optimal scheduling algorithm (like the deadline driven scheduling algorithm EDF) in a preemptive context on uniprocessor systems. We compare the transaction model to the family of multiframe models, then present the exact, and approximated methods, as well as a tunable method to compute the RTA. Finally we present a new schedulability analysis method and an efficient algorithm to speed up this test. © 2012 Springer Science+Business Media, LLC.


Hrazdira A.,Brno University of Technology | Cela A.,School of Engineering in Information and Communication Science and Technology | Hamouche R.,School of Engineering in Information and Communication Science and Technology | Reama A.,School of Engineering in Information and Communication Science and Technology | And 3 more authors.
IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC | Year: 2012

In this paper we present an Optimal Real Time Navigation System (ORTNS) implemented on an Android Smart Device capable of calculating the route to destination based on a permanent Internet connection and information flow obtained from SYTADIN, a traffic Information System. A multi-objective criterion is defined in order to offer the drivers different route to destination parameterization. The ORTNS is not only capable of optimal route to destination calculation with respect to traffic state but also makes the vehicle On-Board energy optimization and/or gas emission reduction possible. As an application example we propose a real time energy management for a Hybrid Electrical Vehicle (HEV) composed of batteries and Super-Capacitors (SC). Based on calculated 3D route to destination and average speeds for each road segment the state of charge (SOC) for batteries and Super-Capacitors (SC) for each receding horizon are optimaly predicted and modified in real time. © 2012 IEEE.


Jurik T.,School of Engineering in Information and Communication Science and Technology | Jurik T.,Brno University of Technology | Cela A.,School of Engineering in Information and Communication Science and Technology | Cela A.,Supelec | And 5 more authors.
IEEE Intelligent Transportation Systems Magazine | Year: 2014

The rapid development of Mobile Internet and Smart Devices and advent of a new generation of Intelligent Transportation Systems (ITS) increase information about present driving conditions and make its prediction possible. Real time traffic information systems (TIS) like SYTADIN help in route to destination planning and traffic state prediction. Energy-optimal routing for electric vehicles creates novel algorithmic challenges where the computation complexity and the quality of information on traffic state are the main issues. This complexity is induced by the possible negative values of edge energy as well as the variability of route and vehicle variables which render the standard algorithms unsuitable. In this paper we present an Energy Optimal Real Time Navigation System (EORTNS), implemented on Samsung Galaxy Tab, capable of calculating the route to destination based on information flow obtained from SYTADIN. As an application example we propose a real time energy management for a Hybrid Electrical Vehicle (HEV) composed of batteries and Super-Capacitors (SC). The EORTNS is not only capable of energy optimal route to destination calculation with respect to traffic state but also operates the On-Board power splitting between batteries and Super-Capacitors. © 2009-2012 IEEE.


Jebai A.K.,Akka Technologies | Combes P.,MINES ParisTech | Malrait F.,MINES ParisTech | Martin P.,Toshiba Corporation | Rouchon P.,Akka Technologies
Proceedings of the IEEE Conference on Decision and Control | Year: 2014

We propose a new approach to modeling electrical machines based on energy considerations and construction symmetries of the motor. We detail the approach on the Permanent-Magnet Synchronous Motor and show that it can be extended to Synchronous Reluctance Motor and Induction Motor. Thanks to this approach we recover the usual models without any tedious computation. We also consider effects due to non-sinusoidal windings or saturation and provide experimental data. © 2014 IEEE.


Toumi A.,Laboratory for Plasma and Conversion of Energy | Chhun L.,AKKA Technologies | Bhosle S.,Laboratory for Plasma and Conversion of Energy | Zissis G.,Laboratory for Plasma and Conversion of Energy | And 5 more authors.
IEEE Transactions on Industry Applications | Year: 2013

This paper presents a numerical model of high-pressure sodium (HPS) lamps, including acoustic streaming. The model is implemented in COMSOL and is based on the finite-element method using a 2-D axisymmetric geometry. Moreover, a revision concerning experimental acoustic resonance (AR) characterizations of HPS lamps will be also provided. The results presented in this paper will contribute to the understanding of AR phenomena and will help in the electronic ballast design methods for AR avoidance. © 1972-2012 IEEE.


Jurik T.,School of Engineering in Information and Communication Science and Technology | Cela A.,School of Engineering in Information and Communication Science and Technology | Hamouche R.,School of Engineering in Information and Communication Science and Technology | Reama A.,School of Engineering in Information and Communication Science and Technology | And 4 more authors.
IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC | Year: 2013

Real time traffic information systems like SYTADIN[11] help in route to destination planning and traffic state prediction. Energy-optimal routing for electric vehicles creates novel algorithmic challenges where the computation complexity is the main issue. This complexity is induced by the possible negative values of edge energy as well as the variability of route and vehicle variables which render the standard algorithms unsuitable (inapplicable). In this paper we present an Energy Optimal Real Time Navigation System (EORTNS), implemented on Samsung Galaxy Tab, capable of calculating the route to destination based on a information flow obtained from SYTADIN. As an application example we propose a real time energy management for a Hybrid Electrical Vehicle (HEV) composed of batteries and Super-Capacitors (SC). The EORTNS is not only capable of energy optimal route to destination calculation with respect to traffic state but also operates the On-Board power splitting between batteries and Super-Capacitors. Based on calculated 3D energy optimal route to destination and average speeds for each road segment as well as the vehicle model the state of charge (SOC) of batteries and Super-Capacitors for each receding horizon are predicted and modified in real time. © 2013 IEEE.


Kedji K.A.,Toulouse 1 University Capitole | Lbathd R.,Toulouse 1 University Capitole | Coulette B.,Toulouse 1 University Capitole | Nassar M.,Mohammed V University | And 2 more authors.
2012 International Conference on Software and System Process, ICSSP 2012 - Proceedings | Year: 2012

Software engineering projects are highly collaborative. Existing tools designed to support collaboration usually provide some specific service, and integration with other tools using data and events. However, Process-Centered Software Engineering Environments have traditionally been designed with different assumptions. The process is usually considered as the central aspect of the software project, and used as a center of control. As a result, great emphasis has been placed on the ability of PSEEs to invoke other tools, or use data generated by other tools. However, the integration in the other direction, that is, the ability of other tools to query the data managed by PSEEs (the process model), and hook into their extensions points, has been largely ignored, as it is not compatible with the vision of the PSEE as the central orchestrator of project support tools. We argue that this view has hindered the widespread adoption of process-based collaboration support tools by incurring too much adoption and switching costs, and propose a new process-based collaboration support architecture, backed by a process metamodel, which can easily be integrated with existing tools. © 2012 IEEE.


Kedji K.A.,Toulouse 1 University Capitole | Lbath R.,Toulouse 1 University Capitole | Coulette B.,Toulouse 1 University Capitole | Nassar M.,Mohammed V University | And 2 more authors.
Journal of Software: Evolution and Process | Year: 2014

Collaboration in software engineering projects is usually intensive and requires adequate support by well-integrated tools. However, process-centered software engineering environments (PSEE) have traditionally been designed to exploit integration facilities in other tools, while offering themselves little to no such facilities. This is in line with the vision of the PSEE as the central orchestrator of project support tools. We argue that this view has hindered the widespread adoption of process-based collaboration support tools by incurring too much adoption and switching costs. We propose a new process-based collaboration support architecture, backed by a process metamodel, that can easily be integrated with existing tools. The proposed architecture revolves around the central concepts of ‘deep links’ and ‘hooks’. Our approach is validated by analyzing a collection of open-source projects, and integration utilities based on the implemented process model server have been developed. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.


Moezzi K.,AKKA Technologies | Aghdam A.G.,Concordia University at Montréal
International Journal of Robust and Nonlinear Control | Year: 2015

In this paper, sufficient conditions are provided for the stability of switched retarded and neutral time-delay systems with polytopic-type uncertainties. It is assumed that the delay in the system dynamics is time-varying and bounded. Parameter-dependent Lyapunov functionals are employed to obtain criteria for the exponential stability of the system in the form of linear matrix inequality (LMI). Free-weighting matrices are then provided to express the relationship between the system variables and the terms in the Leibniz-Newton formula. Numerical examples are presented to show the effectiveness of the results. Copyright © 2014 John Wiley & Sons, Ltd.

Loading Akka Technologies collaborators
Loading Akka Technologies collaborators