Simultaneous optical diagnostic velocity and scalar field by molecular tagging technique Stratified Flames View project

International audienc

Analyse par ondelettes des signaux asymptotiques : Emploi de la phase stationnaire

La représentation en ondelettes décrit un signal à une combinaison linéaire d'ondes changées d'échelle et décalées. Elle s'interprète comme une fonction d'interambiguïté. POur les signaux asymptotiques le module de la transformée se concentre autour d'une arête définissant le "squelette" de la représentation. Elle permet néanmoins la reconstitution approchée du signal avec une grande qualité. Ces propriétés sont utiles pour interpréter les récepteurs des systèmes SONARS animaux

TRAITEMENT DES SIGNAUX ACOUSTIQUES ASYMPTOTIQUES PAR REPRÉSENTATION TEMPS-ÉCHELLE

Time Scale Representation display the energy of analytic signals as a function of time and dilation ratio. These representation are derived using the covarlance properties for time scaling and delay. Asymptotic signals may be easily interpreted when transformed by frequency transformation related to time parity. Acoustic effects related to various media are represented by such transformations.La Représentation Temps Echelle distribue l'énergie des signaux dans le plan des dates et des taux d'hémothétie. Elle utilise la covarlance par changement d'échelle. Dans le cas des signaux asymptotlques la transformation fréquentielle équivalente à la parité possède une Interprétation commode vu certains effets acoustiques observés dans le canal sous marin

Memory effect on biofilm development: biofilm history stronger than environmental conditions

International audienceHydrodynamic conditions are one key parameter acting on biofilms. It is commonly assumed that hydrodynamic conditions shape biofilm morphology by inducing sloughing events, erosion or compression (Van Loosdrecht et al. 2002). Biofilm community structure can also directly or indirectly be influenced by hydrodynamics conditions (Rochex et al. 2008). But it remains unclear if a change in hydrodynamic conditions affects mature biofilm morphology and/or community structure. In the literature, biofilms are mainly studied either under constant shear, e.g. comparing two reactors where biofilms developed at two different shear rates, or as erosion tests as in Paul et al (2012) . In our study, we exposed biofilms to variable hydrodynamic conditions where the applied shear changed over time. Once matured, we exchanged biofilms with different shear histories and exposed them to a change in the hydrodynamic conditions. By this way, it is possible to study the adaptation of physical and microbiological structures of biofilms after a switch in the hydrodynamic conditions

Kinetic modeling of dry anaerobic co-digestion of Lignocellulosic Biomass

Anaerobic digestion is a widely used conversion process for recovering energy from bio degradable waste materials. Dry anaerobic co-digestion of lignocellulosic biomass such as rice straw (RS) with cow dung (CD) offers various benefits other than mono digestion or liquid state anaerobic digestion. However dry anaerobic co-digestion of lignocellulosic biomass has restrictions due to low moisture content and retarded mass transfer within the mixture of substrates which contains in the reactor. Three consecutive batch experiments (E- 1, E-2, and E-3) were conducted by reusing solid digestate of E- 1 as an inoculum to E-2 and solid digestate of E-2 as an inoculum for E-3 in lab scale reactors using RS and CD as substrates. In E-1, CD was the only inoculum and it acted as a substrate as well. Total solids (TS) content of the substrate mixtures of E-1, E-2 and E-3 were 15%, 16%, and 20% respectively. Then mathematical modeling was applied to estimate kinetic parameters related to dry anaerobic co-digestion process using the modified Gompertz model for the three experiments. Modified Gompertz model very closely predicted the ultimate methane yield (Mmax) with R2 almost 0.99 in each scenario. Degradation kinetics improved drastically with the strategy of reusing of digestate, as for the E-2 the lag phase period (λ) reduced from 14 days to almost zero. Ultimate methane yield increased by 104% through this approach. Degradation kinetics were negatively affected with the increase of TS% within the substrate mixture even though digestate was reused as an inoculum. In E-3 ultimate methane yield was 138 ml/g volatile solids (VS) which was a 38% reduction compared to E-2, even though digestate was used as the main inoculum source for the both experiments. But it was a 27% increase compared to E-1 which CD was used as the only inoculum

Control of start-up and operation of anaerobic biofilm reactors: An overview of 15 years of research

International audienceAnaerobic biofilm reactors have to be operated in a way that optimizes on one hand the start-up period by a quick growth of an active biofilm, on the other hand the regular operation by an active control of the biofilm to avoid diffusion limitations and clogging. This article is an overview of the research carried out at INRA-LBE for the last 15 years. The start-up of anaerobic biofilm reactors may be considerably shortened by applying a short inoculation period (i.e. contact between the inoculum and the support media). Then, the increase of the organic loading rate should be operated at a short hydraulic retention time and low hydrodynamic constraints in order to favor biofilm growth. After the start-up period, biofilm growth should be controlled to maintain a high specific activity and prevent clogging. This can be done in particulate biofilm systems by using hydrodynamics to increase or decrease shear forces and attrition but is much more difficult in anaerobic fixed bed reactors

Simultaneous optical diagnostic velocity and scalar field by molecular tagging technique Stratified Flames View project

International audienc

Biomass hydrolysis during solid state dark fermentation: effect of total solids contents and hydrogen partial pressure

National audienc