Reactive Programming of Simulations in Physics

We consider the Reactive Programming (RP) approach to simulate physical systems. The choice of RP is motivated by the fact that RP genuinely offers logical parallelism, instantaneously broadcast events, and dynamic creation/destruction of parallel components and events. To illustrate our approach, we consider the implementation of a system of Molecular Dynamics, in the context of Java with the Java3D library for 3D visualisation

Statistical data mining for symbol associations in genomic databases

A methodology is proposed to automatically detect significant symbol associations in genomic databases. A new statistical test is proposed to assess the significance of a group of symbols when found in several genesets of a given database. Applied to symbol pairs, the thresholded p-values of the test define a graph structure on the set of symbols. The cliques of that graph are significant symbol associations, linked to a set of genesets where they can be found. The method can be applied to any database, and is illustrated MSigDB C2 database. Many of the symbol associations detected in C2 or in non-specific selections did correspond to already known interactions. On more specific selections of C2, many previously unkown symbol associations have been detected. These associations unveal new candidates for gene or protein interactions, needing further investigation for biological evidence

Periodic optimal control for biomass productivity maximization in a photobioreactor using natural light

We address the question of optimization of the microalgal biomass long term productivity in the framework of production in photobioreactors under the influence of day/night cycles. For that, we propose a simple bioreactor model accounting for light attenuation in the reactor due to biomass density and obtain the control law that optimizes productivity over a single day through the application of Pontryagin's maximum principle, with the dilution rate being the main control. An important constraint on the obtained solution is that the biomass in the reactor should be at the same level at the beginning and at the end of the day so that the same control can be applied everyday and optimizes some form of long term productivity. Several scenarios are possible depending on the microalgae's strain parameters and the maximal admissible value of the dilution rate: bang-bang or bang-singular-bang control or, if the growth rate of the algae is very strong in the presence of light, constant maximal dilution. A bifurcation diagram is presented to illustrate for which values of the parameters these different behaviors occur. Finally, a simple sub-optimal bang-bang strategy is proposed that numerically achieves productivity levels that almost match those of the optimal strategy

Rotating disk electrodes to assess river biofilm thickness and elasticity

The present study examined the relevance of an electrochemical method based on a rotating disk electrode (RDE) to assess river biofilm thickness and elasticity. An in situ colonisation experiment in the River Garonne (France) in August 2009 sought to obtain natural river biofilms exhibiting differentiated architecture. A constricted pipe providing two contrasted flow conditions (about 0.1 and 0.45 m s−1 in inflow and constricted sections respectively) and containing 24 RDE was immersed in the river for 21 days. Biofilm thickness and elasticity were quantified using an electrochemical assay on 7 and 21 days old RDE-grown biofilms (t7 and t21, respectively). Biofilm thickness was affected by colonisation length and flow conditions and ranged from 36 ± 15 μm (mean ± standard deviation, n = 6) in the fast flow section at t7 to 340 ± 140 μm (n = 3) in the slow flow section at t21. Comparing the electrochemical signal to stereomicroscopic estimates of biofilms thickness indicated that the method consistently allowed (i) to detect early biofilm colonisation in the river and (ii) to measure biofilm thickness of up to a few hundred μm. Biofilm elasticity, i.e. biofilm squeeze by hydrodynamic constraint, was significantly higher in the slow (1300 ± 480 μm rpm1/2, n = 8) than in the fast flow sections (790 ± 350 μm rpm1/2, n = 11). Diatom and bacterial density, and biofilm-covered RDE surface analyses (i) confirmed that microbial accrual resulted in biofilm formation on the RDE surface, and (ii) indicated that thickness and elasticity represent useful integrative parameters of biofilm architecture that could be measured on natural river assemblages using the proposed electrochemical method

Interval observers for linear time-invariant systems with disturbances

International audienceIt is shown that, for any time-invariant exponentially stable linear system with additive disturbances, time-varying exponentially stable interval observers can be constructed. The technique of construction relies on the Jordan canonical form that any real matrix admits and on time-varying changes of coordinates for elementary Jordan blocks which lead to cooperative linear systems. The approach is applied to detectable linear systems

ANALYSE DES DEFAUTS POUR L'AMELIORATION DE LA QUALITE (ADAQ)

International audienceToutes les entreprises industrielles sont régulièrement confrontées à des problèmes qualité produits. Afin de les résoudre, les techniciens mettent en œuvre une démarche de résolution de problèmes souvent fondée sur une approche expérimentale. Malheureusement cette approche est souvent très empirique et manque généralement de formalisme. L'objectif principal du travail que nous proposons de réaliser est de rationaliser et de formaliser une démarche dans la résolution de problèmes qualité en atelier appelée ADAQ (Analyse des Défauts pour l'Amélioration de la Qualité). Cette méthode devra permettre de converger plus rapidement vers la source du problème et fournira un guide d'utilisation des différentes méthodes d'analyse de données ou d'expérimentation (régression multiple, plans d'expériences, analyse de la variance,...). L'idée est de faire en quelque sorte une AMDEC (Analyse des Modes de Défaillance, de leurs Effets et de leur Criticité) mais qui serait déclenchée chaque fois qu'un défaut apparaît en production

European Spatial Politics and Spatial Policy for Europe:<br />an analysis of some notions.

This paper deals with notions of European spatial planning. Some of them are analysed thanks to the theoretical framework of complexity. For us, the notions involved in the definition of policies are also the product of a political process. What is more, we think that the “quality” of these notions relies on their ability (more precisely, the ability of the actors which are using them) to combine policy making and political process and constraints in a rather unpredictable way that generate different interpretations and different results

Stability analysis of a wastewater treatment plant with saturated control

International audienceThis paper presents a saturated proportional controller that achieves depollution of wastewater in a continuous anaerobic digester. This goal is reached by defining a region of the state-space where the depollution is achieved and forcing attractivity and invariance of this region. The control variable is the dilution rate and the controlled variable is a linear combination (S λ) of the substrates con-centrations, that could be the Chemical Oxygen Demand (COD) or the Biological Oxygen Demand (BOD), depending on the value of λ. No measurement of the substrates concentrations in the input flow is required; the only necessary measurement is S λ