Low rank approximation of multidimensional data

In the last decades, numerical simulation has experienced tremendous improvements driven by massive growth of computing power. Exascale computing has been achieved this year and will allow solving ever more complex problems. But such large systems produce colossal amounts of data which leads to its own difficulties. Moreover, many engineering problems such as multiphysics or optimisation and control, require far more power that any computer architecture could achieve within the current scientific computing paradigm. In this chapter, we propose to shift the paradigm in order to break the curse of dimensionality by introducing decomposition to reduced data. We present an extended review of data reduction techniques and intends to bridge between applied mathematics community and the computational mechanics one. The chapter is organized into two parts. In the first one bivariate separation is studied, including discussions on the equivalence of proper orthogonal decomposition (POD, continuous framework) and singular value decomposition (SVD, discrete matrices). Then, in the second part, a wide review of tensor formats and their approximation is proposed. Such work has already been provided in the literature but either on separate papers or into a pure applied mathematics framework. Here, we offer to the data enthusiast scientist a description of Canonical, Tucker, Hierarchical and Tensor train formats including their approximation algorithms. When it is possible, a careful analysis of the link between continuous and discrete methods will be performed.IV Research and Transfer Plan of the University of SevillaInstitut CarnotJunta de AndalucíaIDEX program of the University of Bordeau

Model Order Reduction in Fluid Dynamics: Challenges and Perspectives

This chapter reviews techniques of model reduction of fluid dynamics systems. Fluid systems are known to be difficult to reduce efficiently due to several reasons. First of all, they exhibit strong nonlinearities — which are mainly related either to nonlinear convection terms and/or some geometric variability — that often cannot be treated by simple linearization. Additional difficulties arise when attempting model reduction of unsteady flows, especially when long-term transient behavior needs to be accurately predicted using reduced order models and more complex features, such as turbulence or multiphysics phenomena, have to be taken into consideration. We first discuss some general principles that apply to many parametric model order reduction problems, then we apply them on steady and unsteady viscous flows modelled by the incompressible Navier-Stokes equations. We address questions of inf-sup stability, certification through error estimation, computational issues and — in the unsteady case — long-time stability of the reduced model. Moreover, we provide an extensive list of literature references

Gestion des ecosystemes forestiers denses d'Afrique tropicale humide: 2. Congo

This bibliography for the Republic of Congo is a sequel to the one on Gabon. It comprises 312 annotated references on thematic areas: fauna, flora, vegetation, ecology, conservation, silviculture, forest inventory, forest management, forest policy and economy, non-timber forest products, etc.; and a 20-page presentation of the country and its forests

Comparison of an effect-model-law-based method versus traditional clinical practice guidelines for optimal treatment decision-making: application to statin treatment in the French population

Healthcare authorities make difficult decisions about how to spend limited budgets for interventions that guarantee the best cost-efficacy ratio. We propose a novel approach for treatment decision-making, OMES—in French: Objectif thérapeutique Modèle Effet Seuil (in English: Therapeutic Objective–Threshold–Effect Model; TOTEM). This approach takes into consideration results from clinical trials, adjusted for the patients' characteristics in treatment decision-making. We compared OMES with the French clinical practice guidelines (CPGs) for the management of dyslipidemia with statin in a computer-generated realistic virtual population, representing the adult French population, in terms of the number of all-cause deaths avoided (number of avoided events: NAEs) under treatment and the individual absolute benefit. The total budget was fixed at the annual amount reimbursed by the French social security for statins. With the CPGs, the NAEs was 292 for an annual cost of 122.54 M€ compared with 443 with OMES. For a fixed NAEs, OMES reduced costs by 50% (60.53 M€ yr(−1)). The results demonstrate that OMES is at least as good as, and even better than, the standard CPGs when applied to the same population. Hence the OMES approach is a practical, useful alternative which will help to overcome the limitations of treatment decision-making based uniquely on CPGs

La neutralité en termes de dégradation des terres

Fiche d'actualitéLa dégradation des terres constitue un frein au développement durable en impactant l’environnement, la sécurité alimentaire, la fourniture de services par les agroécosystèmes et les conditions de vie des populations. C’est un problème à la fois local, régional et global, qui touche autant les zones sèches que le reste du monde. Dès lors, un effort global, concerté, visant à enrayer et inverser ce phénomène, s’impose. Face à cette situation, la neutralité en termes de dégradation est apparue comme un nouveau concept mobilisateur pour la communauté internationale

La neutralité en termes de dégradation des terres

Fiche d'actualitéLa dégradation des terres constitue un frein au développement durable en impactant l’environnement, la sécurité alimentaire, la fourniture de services par les agroécosystèmes et les conditions de vie des populations. C’est un problème à la fois local, régional et global, qui touche autant les zones sèches que le reste du monde. Dès lors, un effort global, concerté, visant à enrayer et inverser ce phénomène, s’impose. Face à cette situation, la neutralité en termes de dégradation est apparue comme un nouveau concept mobilisateur pour la communauté internationale

La neutralité en termes de dégradation des terres

Fiche d'actualitéLa dégradation des terres constitue un frein au développement durable en impactant l’environnement, la sécurité alimentaire, la fourniture de services par les agroécosystèmes et les conditions de vie des populations. C’est un problème à la fois local, régional et global, qui touche autant les zones sèches que le reste du monde. Dès lors, un effort global, concerté, visant à enrayer et inverser ce phénomène, s’impose. Face à cette situation, la neutralité en termes de dégradation est apparue comme un nouveau concept mobilisateur pour la communauté internationale