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Dakar, Senegal

El Saadi N.,LAMOPS | Bah A.,UMI 209
Journal of Biological Systems | Year: 2015

In this paper, we are interested in the numerical simulation of a nonlinear stochastic partial differential equation (SPDE) arising as a model of phytoplankton aggregation. This SPDE consists of a diffusion equation with a chemotaxis term and a branching noise. We develop and implement a numerical scheme to solve this SPDE and present its numerical solutions for parameter values corresponding to real conditions in nature. Further, a comparison is made with two deterministic versions of the SPDE, that are advection-diffusion equations with linear and nonlinear reaction terms, to emphasize the efficiency of the stochastic equation in modeling the aggregation behavior in phytoplankton. © 2015 World Scientific Publishing Company. Source

El Saadi N.,Cread | Bah A.,UMI 209 | Belarbi Y.,Cread
Studies in Computational Intelligence | Year: 2010

The problem of internal migration and its effect on urban unemployment and underemployment has been the subject of an abundant theoretical literature on economic development. However, most discussions have been largely qualitative and have not provided enough rigorous frame-works with which to analyze the mechanism of labor migration and urban unemployment. In this paper, we build up an economic behavioral model of rural-urban migration which is an agent-based version of the analytical Todaro model described by deterministic ordinary differential equations. The agent-based model allows to explore the rural-urban labor migration process and give quantitative results on the equilibrium proportion of the labor force that is not absorbed by the modern industrial economy. © 2010 Springer-Verlag Berlin Heidelberg. Source

Le V.-M.,Vietnam National University, Hanoi | Chevaleyre Y.,CNRS Informatics Laboratory of Paris Nord | Zucker J.-D.,UMI 209 | Vinh H.T.,Vietnam National University, Hanoi
Lecture Notes in Business Information Processing | Year: 2014

Nowadays, most coastal regions face a potential risk of tsunami. Most of researches focus on people evacuation. However, there are always the part of evacuees (e.g. the tourist) who lack information of the city map, we then focus on the solution to guide people in evacuation. With regards to the guiding system in evacuation, most of the studies focus on the placement of guidance signs. In fact, in panic situation the evacuees can get lost if the they do not receive guidance signs at a certain crossroad or corner. Then, if there are not enough signs at every crossroad or corner on a certain path to the safe places (called shelters), the guidance signs will become useless. In order to give evacuees a complete guidance of evacuation, we propose to place the local evacuation maps which highlight the shortest path from a place (where the panel of the map is placed) to the nearest shelter. At specific places in the city, once this kind of map is perceived, the evacuees should follow the shortest evacuation path to shelters. In this paper, we first present the method to optimize the local evacuation maps by using the genetic algorithm on candidate locations of the maps and the evaluating the percentage survivors as fitness. We then present two approaches to evaluate the fitness: one uses the agent-based simulation and other uses the linear programming formulation. By experimentation, our proposed approaches showed better results the approach of optimizing sign placement in the same scenario. © Springer International Publishing Switzerland 2014. Source

Le V.-M.,Vietnam National University, Hanoi | Chevaleyre Y.,CNRS Informatics Laboratory of Paris Nord | Zucker J.-D.,UMI 209 | Vinh H.T.,Vietnam National University, Hanoi
Proceedings - 2013 RIVF International Conference on Computing and Communication Technologies: Research, Innovation, and Vision for Future, RIVF 2013 | Year: 2013

Nowadays, tsunami is becoming one of the most dangerous natural disaster for coastal regions. Along with the early warning system, evacuation is one of the first mitigation procedures to consider. The evacuation simulation then received a lot of studies in recent years in the domain of computer science. In fact, there are always the part of evacuees (e.g. the tourist) who lack information of the evacuation map, which motivates us to study the problem of optimizing of guidance sign placement for tsunami evacuation. In this paper, we first propose the approach of Linear Programming that speeds up the Evaluation of Casualties in Agent-based Simulation in order to overcome the problem of computational speed of agent-based simulation. Then, we present an approach for optimizing the sign placement by using genetic algorithm with the fitness evaluated by the agent-based simulation. © 2013 IEEE. Source

Yafia R.,University Ibn Zohr | Aziz-Alaoui M.A.,Normandie University | Aziz-Alaoui M.A.,French National Center for Scientific Research | Merdan H.,TOBB University of Economics and Technology | Tewa J.J.,UMI 209
International Journal of Bifurcation and Chaos | Year: 2015

The model analyzed in this paper is based on the model set forth by Aziz Alaoui et al. [Aziz Alaoui & Daher Okiye, 2003; Nindjin et al., 2006] with time delay, which describes the competition between the predator and prey. This model incorporates a modified version of the Leslie-Gower functional response as well as that of Beddington-DeAngelis. In this paper, we consider the model with one delay consisting of a unique nontrivial equilibrium E∗and three others which are trivial. Their dynamics are studied in terms of local and global stabilities and of the description of Hopf bifurcation at E∗. At the third trivial equilibrium, the existence of the Hopf bifurcation is proven as the delay (taken as a parameter of bifurcation) that crosses some critical values. © 2015 World Scientific Publishing Company. Source

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