Time filter

Source Type

Yasso I.,Numerical modelling of fluid mechanics the environment | Gueraoui K.,University of Ottawa | Niazi A.,school Hassania of Casablanca | Zeggwagh G.,Laboratory of applied mathematics
International Review of Mechanical Engineering | Year: 2010

This article presents the development of a law of visco-elastic behaviour with one-sided damage for the bituminous materials, based on the observation of the essays of direct break on film of asphalt between two hemispheres of metal. The essays of fatigue of the bituminous materials realized on test tubes lead a loss of rigidity combined in a significant extension of test tubes at the beginning of the essay for strong levels of solicitation. It will also present a structure design of the asphalt pavement in Japan. © 2010 Praise Worthy Prize S.r.l.- All right reserved.


Yasso I.,URAC 13 | Gueraoui K.,University of Ottawa | Niazi A.,School Hassania of Casablanca | Zeggwagh G.,Laboratory of applied mathematics
International Review on Modelling and Simulations | Year: 2010

This article is in the context of the dimensioning methods of the flexible pavement. It concentrates on the problems of the taking into account of the loads of traffic according to the probabilistic parameters of the temperature, particularly for the analytical or incremental methods. After having presented the method of characterization of the bitumen binders according to their viscoelastic behavior to Morocco and Japan and the factors influencing the bearing capacity between these two countries. We are interested this time in dimensioning of a Moroccan flexible pavement with the incremental method of Japan. In these last, the deformations due to the loads of traffic, given on the basis of linear elastic modeling of the roadways (model of Burmister), are used for the estimate of the lifespan of the roadway. The real loads of traffic of the roadways are diversified of an area with another, as well on the level of their intensity as of their mode of application. It is through this vision of globalization that a comparison between the various models of dimensioning in particular between Morocco and Japan is carried out. Morocco although with these great geographical extents is a country which strongly depends on the climatic risks and although since a certain number of years of vast construction projects of new roadways and handing-over on level of the old roads are launched; one of the disadvantages major of this vast policy is the cost. The comparison compared to Japan seems interesting in measurement or although this country is classified among most advanced economically world, the problems are much more important in measurement or the materials rare on the one hand and are very regulated compared to the environmental laws on the other hand. Thus, it will be a question of presenting the philosophy of Japanese design pavements. Once this solved stage, it will be necessary to adapt methodology to the Moroccan model (drawn from the Moroccan catalog of pavement design) and to check the state of the constraints and deformations under imposed requests. Conclusions and prospects compared to the pavement design could be brought thereafter in order to improve the current methods of pavement design in Morocco. © 2010 Praise Worthy Prize S.r.l.-All rights reserved.


Blehaut H.,Institute Jerome Lejeune | Mircher C.,Institute Jerome Lejeune | Ravel A.,Institute Jerome Lejeune | Conte M.,Institute Jerome Lejeune | And 7 more authors.
PLoS ONE | Year: 2010

Background: Seven genes involved in folate metabolism are located on chromosome 21. Previous studies have shown that folate deficiency may contribute to mental retardation in Down's syndrome (DS). Methodology: We investigated the effect of oral folate supplementation (daily dose of 1.0±0.3 mg/kg) on cognitive functions in DS children, aged from 3 to 30 months. They received 1 mg/kg leucovorin or placebo daily, for 12 months, in a single-centre, randomised, double-blind study. Folinic acid (leucovorin, LV) was preferred to folic acid as its bioavailability is higher. The developmental age (DA) of the patients was assessed on the Brunet-Lezine scale, from baseline to the end of treatment. Results: The intent-to-treat analysis (113 patients) did not show a positive effect of leucovorin treatment. However, it identified important factors influencing treatment effect, such as age, sex, and concomitant treatments, including thyroid treatment in particular. A per protocol analysis was carried out on patients evaluated by the same examiner at the beginning and end of the treatment period. This analysis of 87 patients (43 LV-treated vs. 44 patients on placebo) revealed a positive effect of leucovorin on developmental age (DA). DA was 53.1% the normal value with leucovorin and only 44.1% with placebo (p<0.05). This positive effect of leucovorin was particularly strong in patients receiving concomitant thyroxin treatment (59.5% vs. 41.8%, p<0.05). No adverse event related to leucovorin was observed. Conclusion: These results suggest that leucovorin improves the psychomotor development of children with Down's syndrome, at least in some subgroups of the DS population, particularly those on thyroxin treatment. Trial Registration: Clinical Trials.gov, NCT00294593 © 2010 Blehaut et al.


Takoutsing E.,University of Dschang | Bowong S.,Laboratory of Applied Mathematics | Yemele D.,University of Dschang | Kurths J.,Potsdam Institute for Climate Impact Research
International Journal of Bifurcation and Chaos | Year: 2014

In this paper, we develop a mathematical model to assess the strength of the effects of catastrophic anemia level on the dynamical transmission of malaria parasite within the body of a host. We first consider a temporal model. The important mathematical features of the model are thoroughly investigated. We found that the model exhibits forward bifurcation. We also consider a spatiotemporal model using reaction-diffusion equations. The model is numerically analyzed to assess the impact of anemia on the dynamical transmission of malaria parasite within the body of a host. Through numerical simulation, we found that malaria can lead to a catastrophic anemia level even if the parasite is nonpersistent within the body of a host. Numerical results also suggest that to reduce or control the anemia level, the strategy should be to accelerate innate cell reproduction rate or should have the ability to clean parasitized red blood cells (PRBCs) with a high mortality rate. © 2014 World Scientific Publishing Company.


Dumbser M.,Laboratory of Applied Mathematics
AIP Conference Proceedings | Year: 2013

We present two new families of better than second order accurate Godunov-type finite volume methods for the solution of nonlinear hyperbolic partial differential equations with nonconservative products. One family is based on a high order Arbitrary-Lagrangian-Eulerian (ALE) formulation on moving meshes, which allows to resolve the material contact wave in a very sharp way when the mesh is moved at the speed of the material interface. The other family of methods is based on a high order Adaptive Mesh Refinement (AMR) strategy, where the mesh can be strongly refined in the vicinity of the material interface. Both classes of schemes have several building blocks in common, in particular: a high order WENO reconstruction operator to obtain high order of accuracy in space; the use of an element-local space-time Galerkin predictor step which evolves the reconstruction polynomials in time and that allows to reach high order of accuracy in time in one single step; the use of a path-conservative approach to treat the nonconservative terms of the PDE. We show applications of both methods to the Baer-Nunziato model for compressible multiphase flows. © 2013 AIP Publishing LLC.


Yasso I.,British Petroleum | Gueraoui K.,British Petroleum | Gueraoui K.,University of Ottawa | Niazi A.,School Hassania | Hammoumi A.,Laboratory of applied mathematics
International Review of Mechanical Engineering | Year: 2010

In this article, we go in a comparative way, to study the various factors influencing the bearing capacity of the bitumen binders. In fact the factors which will be quoted in the continuation are the loads of circulation and their effects with short, average and long run on the roadways, inevitably inducing the phenomenon of rutting, the composition of materials of the various layers of the roadway, the climatic conditions, and of the geometry of the roadway. Fundamental and well established concepts these factors in Morocco and Japan are mainly described, these fundamental are, for the majority based on the experiment May in Japan a new law of behaviour based on the dissipation of energy was introduced.les factors of traffic and the climatic effects were built-in a system as being probabilistic variables. In this system it is allowed that the tiredness of the bituminous mix is with the outsides and interior bituminous mix. Be factors influencing measurement and the theoretical analysis of clearance is also described briefly. Thus, the development of a new type of asphalt of great viscosity is presented. The idea being to regulate as soon as possible in Japan, permanent deformations due to the effects of the sharp variations of temperatures and by the loads due to the traffic of the heavy trucks which becomes increasingly important. The use of this new type of asphalt made this evidence, reason for which, it would be interesting that a country like Morocco with cities like Marrakech, Rabat, Casablanca and presenting important heat gradients (Marrakech, Rabat, and Casablanca) should be based on the Japanese experiment in order to improve the characteristics of the bituminous mixes. © 2010 Praise Worthy Prize S.r.l. - All rights reserved.


Zanotti O.,Laboratory of Applied Mathematics | Dumbser M.,Laboratory of Applied Mathematics
Physics of Fluids | Year: 2015

We study the Richtmyer-Meshkov (RM) instability of a relativistic perfect fluid by means of high order numerical simulations with adaptive mesh refinement (AMR). The numerical scheme combines a finite volume reconstruction in space, a local space-time discontinuous Galerkin predictor method, a high order one-step time update scheme, and a "cell-by-cell" space-time AMR strategy with time-accurate local time stepping. In this way, third order accurate (both in space and in time) numerical simulations of the RM instability are performed, spanning a wide parameter space. We present results both for the case in which a light fluid penetrates into a higher density one (Atwood number A > 0) and for the case in which a heavy fluid penetrates into a lower density one (Atwood number A < 0).We find that for large Lorentz factors γs of the incident shock wave, the relativistic RM instability is substantially weakened and ultimately suppressed. More specifically, the growth rate of the RM instability in the linear phase has a local maximum which occurs at a critical value of γs ≈ [1.2,2]. Moreover, we have also revealed a genuinely relativistic effect, absent in Newtonian hydrodynamics, which arises in three dimensional configurations with a non-zero velocity component tangent to the incident shock front. In particular, in A > 0 models, the tangential velocity has a net magnification effect, while in A < 0 models, the tangential velocity has a net suppression effect. © 2015 AIP Publishing LLC.


Zanotti O.,Laboratory of Applied Mathematics | Dumbser M.,Laboratory of Applied Mathematics | Fambri F.,Laboratory of Applied Mathematics
Journal of Physics: Conference Series | Year: 2016

We describe a new method for the solution of the ideal MHD equations in special relativity which adopts the following strategy: (i) the main scheme is based on Discontinuous Galerkin (DG) methods, allowing for an arbitrary accuracy of order N+1, where N is the degree of the basis polynomials; (ii) in order to cope with oscillations at discontinuities, an "a-posteriori" sub-cell limiter is activated, which scatters the DG polynomials of the previous time-step onto a set of 2N+1 sub-cells, over which the solution is recomputed by means of a robust finite volume scheme; (iii) a local spacetime Discontinuous-Galerkin predictor is applied both on the main grid of the DG scheme and on the sub-grid of the finite volume scheme; (iv) adaptive mesh refinement (AMR) with local time-stepping is used. We validate the new scheme and comment on its potential applications in high energy astrophysics.

Loading Laboratory of applied mathematics collaborators
Loading Laboratory of applied mathematics collaborators