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Cergy, France

Mhenni F.,ISMEP | Nguyen N.,EISTI Cergy | Choley J.-Y.,ISMEP
IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM | Year: 2014

In this paper, a methodology is proposed to integrate safety analysis within a systems engineering approach. This methodology is based on SysML models and aims at generating (semi-) automatically safety analysis artifacts, mainly FMEA and FTA, from system models. Preliminary functional and component FMEA are automatically generated from the functional and structural models respectively, then completed by safety experts. By representing SysML structural diagram as a directed multi-graph, through a graph traversal algorithm and some identified patterns, generic fault trees are automatically derived with corresponding logic gates and events. The proposed methodology provides the safety expert with assistance during safety analysis. It helps reducing time and error proneness of the safety analysis process. It also helps ensuring consistency since the safety analysis artifacts are automatically generated from the latest system model version. The methodology is applied to a real case study, the electromechanical actuator EMA. © 2014 IEEE. Source

Leboucher C.,MBDA France | Shin H.-S.,Cranfield University | Siarry P.,UPEC | Le Menec S.,MBDA France | And 2 more authors.
Information Sciences | Year: 2016

This paper proposes an enhanced Particle Swarm Optimisation (PSO) algorithm and examines its performance. In the proposed PSO approach, PSO is combined with Evolutionary Game Theory to improve convergence. One of the main challenges of such stochastic optimisation algorithms is the difficulty in the theoretical analysis of the convergence and performance. Therefore, this paper analytically investigates the convergence and performance of the proposed PSO algorithm. The analysis results show that convergence speed of the proposed PSO is superior to that of the Standard PSO approach. This paper also develops another algorithm combining the proposed PSO with the Standard PSO algorithm to mitigate the potential premature convergence issue in the proposed PSO algorithm. The combined approach consists of two types of particles, one follows Standard PSO and the other follows the proposed PSO. This enables exploitation of both diversification of the particles' exploration and adaptation of the search direction. © 2016 Elsevier Inc. All rights reserved. Source

Nguyen N.,EISTI Cergy
10th Annual International Systems Conference, SysCon 2016 - Proceedings | Year: 2016

Nowadays man-made systems are getting more complex including new technologies and components from different domains. In addition, they are used in many safety critical missions. This induces new challenges in the design of such systems as new methods and tools are needed to manage the complexity while taking into account safety aspects. To face these challenges, the use of model-based approaches such as MBSE is compulsory. In addition, only an efficient integration of safety concerns early in the design process guarantees an optimal design avoiding late and costly changes. Our proposal is an integrated methodology named SafeSysE, including both MBSE and MBSA processes. SafeSysE narrows the gap between the design and safety analyses since it allows to assist the safety expert in generating the safety artifacts such as FMEA and FTA from the system models. It enhances the consistency between the system model including the requirements, structure and behavior of the system in one side and the safety artifacts in the other side. © 2016 IEEE. Source

Barot S.,French National Institute for Agricultural Research | Bornhofen S.,EISTI Cergy | Boudsocq S.,French National Institute for Agricultural Research | Raynaud X.,University Pierre and Marie Curie | Loeuille N.,University Paris Diderot
Functional Ecology | Year: 2015

Evolution of nutrient acquisition by plants should depend on two forces: local competition is based on the capacity to exploit the local nutrient resource, and regional competition is based on the capacity to occupy the whole landscape through seed production and dispersal. We build a spatially explicit simulation model where a limiting nutrient is recycled in each local patch of a lattice by individual plants. The model includes both local and regional competition. Heterogeneity in nutrient availability and dispersal limitation mitigate the effect of competition for the local nutrient resource and allow the evolution of lower rates of nutrient uptake. Our spatially explicit model suggests that evolution in richer ecosystems selects 'expensive' strategies (high acquisition, low conservation of resources) compared to poor ecosystems. Low rates of nutrient acquisition can be considered as a form of altruism because they leave more resource available for other individuals. Our model thus suggests that the influence of spatial processes on the evolution of altruism is pervasive and is linked to key aspects of ecosystem functioning. Because our model includes both regional and local competition, evolution does not minimize the availability of mineral nutrient, although evolution or species replacement is often thought to minimize the availability of nutrient. Taken together, our work confirms that the interplay between local and regional competition is critical for the evolution of plant nutrient strategies and its effect on ecosystem properties. © 2015 British Ecological Society. Source

Bornhofen S.,EISTI Cergy | Barot S.,Ecole Normale Superieure de Paris | Lattaud C.,University of Paris Descartes
Ecological Modelling | Year: 2011

This paper introduces a functional-structural plant model based on artificial life concepts and L-systems. This model takes into account realistic physiological rules, the architecture of the plants and their demography. An original benefit of this approach is that it allows the simulation of plant evolution at both functional and life-history levels implementing mutations to the L-systems and a set of genetic parameter values. The conducted experiments focus on the evolutionary emergence of different life history strategies in an environment with heterogeneous resource availability and disturbance frequency. It is found that, depending on the encountered conditions, the plants develop three major strategies classified as competitors, stress-tolerators and ruderals according to Grime's CSR theory. Most of the evolved characteristics comply with theoretical biology or field observations on natural plants. Besides these results, our modelling framework is highly flexible and many refinements can be readily implemented depending on the issues one intends to address. Moreover, the model can readily be used to address many questions at the interface between evolutionary ecology, plant functional and community ecologies and ecosystem ecology. © 2010 Elsevier B.V. Source

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