Scalable Design Space Exploration via Answer Set Programming

The design of embedded systems is becoming continuously more complex such that the application of efficient high level design methods are crucial for competitive results regarding design time and performance. Recently, advances in Boolean constraint solvers for Answer Set Programming (ASP) allow for easy integration of background theories and more control over the solving process. The goal of this research is to leverage those advances for system level design space exploration while using specialized techniques from electronic design automation that drive new application-originated ideas for multi-objective combinatorial optimization

Approche Conceptuelle et Algorithmique des Equilibres de Nash Robustes Incitatifs

On propose une analyse de la robustesse des équilibres de Nash dans le cadre d’un mécanisme Bayésien incitatif. On met en valeur une contrainte de robustesse comme élément de réponse au problème de rationalité individuelle (intermédiaire) selon 1) une approche conceptuelle des propriétés de la solution d’équilibre et 2) une approche algorithmique du protocole et des étapes calculatoires.

Modeling And Applying Biomimetic Metaheuristics To Product Life Cycle Engineering

Due to its potential for significant impact, interest continues to grow in the assessment of products from a life cycle perspective. As the nature of products shifts from mechanized and Newtonian to more adaptive and complex, the behavior of products more closely resembles biological organisms in community. The change in product nature is increasingly mirrored at the component level. The work presented in this dissertation is twofold. First, the research proposes a general, systematic and holistic classification of life cycle data to transform the design problem into an optimization problem. Second, the research proposes two new metaheuristics (bio-inspired and socio-inspired) to solve optimization problems to produce grouped solutions that are efficient, evolvable and sustainable. The bio-inspired approach is schooling genetic algorithms (SGA), while the socio-inspired approach is referred to as genetic social networks (GSN). SGA is an approach that combines fish schooling concepts with genetic algorithms (GAs) to enable a dynamic search process. The application of GA operators is subject to the perception of the immediate local environment by clusters of candidate solutions behaving as schools of fish. GSN is an approach that adds social network concepts to GAs, implementing single and dyadic social interactions of social groups (clusters of similar candidate solutions) with GA operators. SGA and GSN both use phenotypic representations of a hypothetical product or system as input. The representations are derived from the proposed life cycle engineering (LCE) data classification. The outputs of either method are the representations that are more than likely to perform better, longer, and more autonomously within their environment during their life cycle. Both methods can also be used as a decision making tool. Both approaches were tested on product design problems with differing parametric relations, underlying solution space, and problem size

Computing Diverse Optimal Stable Models

We introduce a comprehensive framework for computing diverse (or similar) solutions to logic programs with preferences. Our framework provides a wide spectrum of complete and incomplete methods for solving this task. Apart from proposing several new methods, it also accommodates existing ones and generalizes them to programs with preferences. Interestingly, this is accomplished by integrating and automating several basic ASP techniques - being of general interest even beyond diversification. The enabling factor of this lies in the recent advance of multi-shot ASP solving that provides us with fine-grained control over reasoning processes and abolishes the need for solver modifications and wrappers that were indispensable in previous approaches. Our framework is implemented as an extension to the ASP-based preference handling system asprin. We use the resulting system asprin 2 for an empirical evaluation of the diversification methods comprised in our framework

Simulation des transferts réactifs multi-constituants au sein des lits d’infiltration percolation – évaluation des capacités d’oxygénation

L’assainissement des eaux usées par infiltration percolation appartient à la filière de traitement des rejets polluants à cultures fixées. Dans un contexte géographique spécifique et pour une population avoisinant 500 à 1 000 équivalents habitants, elle paraît bien indiquée. Filière dite rustique, elle n’en est pas moins complexe. L’objectif de cette étude est de contribuer, à travers une simulation numérique, à la compréhension des phénomènes physiques et biochimiques qui s’établissent au sein d’un lit d’infiltration percolation. Les aspects essentiels à l’activité bactérienne que sont l’hydrodynamique du milieu poreux, le développement de la biomasse active, le transport, la consommation et les transferts d’oxygène y sont abordés. À travers des essais d’une vérification méthodique du modèle effectuée à partir des solutions analytiques, il ressort principalement que la dispersion hydrodynamique et le taux de dégradation ont des effets contraires sur le rendement d’abattement des charges polluantes. En outre, un résultat significatif obtenu est la comparaison qualitative et quantitative des apports convectifs et diffusifs en oxygène au sein des lits d’infiltration percolation qui sont à aération naturelle.Wastewater sanitation using infiltration/percolation is part of an approach that uses attached microorganisms to treat pollutant loads. It appears suitable for a specific geographical context, and for population equivalents of approximately 500-1000 people. The aim of this study was to improve, by means of a numerical simulation, the understanding of certain physical and biochemical phenomena observed within an infiltration/percolation bed. All the aspects essential to bacterial activity are examined, including: the hydrodynamics of the porous media; the development of an active biomass; transport; and oxygen transfer and consumption. The latter are of paramount importance in non-saturated porous media, where significant aeration can take place, whereas in saturated soils and aquifers containing nitrogenous and organic compounds, the oxygen in water is rapidly consumed.The model we have formulated includes seven equations, which describe macroscopic transport, and are coupled and non-linear. The terms “wells/sources” are functions of unknown variables. The resolution of the equations, obtained after discretization of the equations using Euler’s finite difference method, was performed using Thomas’ algorithm and Fortran 95 programming. We used an innovative approach: analytical solutions developed for saturated porous media were modified to take into account a heterogeneous flow field in a non-saturated porous medium. In a systematic approach, we tested two problems that are part of a gradual verification process: one-dimensional convection-dispersion solute without a kinetic reaction; one-dimensional solute with a first-order decay.The code we have developed insures a very good approximation of the solute transport within a non-saturated porous medium. For a given rate of flow and a given supply period, the greater the dispersion, the quicker the solute will become homogeneous. In other words, a very high dispersion will induce a very low residence time for the solute within the medium. In wastewater treatment within sand beds, the residence time or contact period between the pollutant matter transported by the effluent and the purifying biomass attached to the support is thus a parameter that is linked to the dispersion of the effluent within the medium. It also appears that the reduction in pollutant load is optimized within a biofilm with a high degradation rate, and for an effluent with a low dispersion coefficient. This result is coherent with the link between dispersion and residence time of the effluent in the system.We also examined the impact that the hydraulic load and the substrate content in the effluent have on the oxygenation capacities of a filtering mass. A qualitative and quantitative analysis of the incoming oxygen flow was performed. Thus we show that, at the beginning of the supply period, convection is more influential than diffusion. We also present several results from the simulations of substrate reduction profiles, which were very closely linked to oxygen content profiles. Thus we observed a rapid decrease in oxygen content due to intensive bacterial activity in the upper part of sand filters, followed by an increase in oxygen towards the bottom of the filter due to the absence of substrate. The main conclusion of this part of the study was that in order to optimize the ability for oxygenation within infiltration/percolation beds, it would be preferable to connect them to the separate sewer networks, which yield more concentrated effluents than do combined sewer networks

Capacités de traitement d'un effluent de synthèse en infiltration percolation

Dans cet article, nous présentons des travaux mettant en évidence les capacités de traitement biologique des eaux résiduaires urbaines au sein des milieux poreux de textures différentes. Une étude comparative du développement de la biomasse couplé aux mécanismes généraux de transferts gazeux à travers deux réacteurs biologiques est menée. Des lits d’infiltration percolation sont simulés par des colonnes garnies de sables d’origine et de structures différentes. Ils sont alimentés périodiquement via un automate de commande avec un influent d’une charge de 525 mgDCO/l et de 54 mgNK/l. Les résultats obtenus établissent le fait qu’un développement équilibré de la biomasse incluant les phases de croissance et de régression est intrinsèquement lié à la nature physique du matériau support. A l’aide des carottes prélevées sur les massifs filtrants et des sondes d’oxymétrie introduites à différentes hauteurs des lits d’infiltration, nous montrons que la répartition verticale du biofilm dans les colonnes ainsi que l’oxygénation des milieux poreux lors des périodes de repos sont également corrélées à la structure des supports pourtant de diamètres moyens similaires. L’efficacité de traitement biologique du carbone est supérieure pour un sable d’origine alluvionnaire comparativement à un sable concassé ; la tendance s’inversant significativement lorsqu’il s’agit de la diminution de l’azote.In this article, we present work highlighting the capacity of variously textured porous media to biologically process urban waste water. A comparative study was undertaken that coupled biomass development with general gas transfer mechanisms through two biological engines.Infiltration/percolation beds are biological systems that treat water using a purifying bacterial culture that develops on a mineral support. Used in domestic wastewater treatment, they are regarded as being well suited to rural areas. These infiltration/percolation beds are easy to use and attain a high quality in their output, two factors that constitute assets for small communities.Infiltration/percolation beds were simulated in the present work by columns lined with sands of varying origin and structure. They were fed automatically, at set intervals, with waste water containing 525 mg/L of dissolved organic carbon (DOC) and 54 mg/L of Kjeldahl nitrogen. A balanced development of the biomass, including the phases of growth and regression, was intrinsically related to the physical nature of the material used as a support. First, during the supply period, balanced growth of the biomass was quickly reached within the crushed sand. Secondly, within round sand, the regression of the biofilm was less significant and more regular over several weeks. In both supports, the regression was well correlated with an exponential decay. Lastly, the frequency of the supply periods, the organic loads involved, and the rest periods imposed are all factors that contribute to a lack of accumulation of living and/or inert organic matter in the columns.After obtaining a balanced development of the biomass, the abilities of the columns to reduce the concentrations of carbon, Kjeldahl nitrogen and ammonia were evaluated. Samples of effluent were taken downstream, both before the beginning of the supply period and as it came out of the column approximately thirty minutes after beginning the drainage period. The percentage of suspended matter coming out of the columns gave rather precise information on the scrubbing of the solid mass caused by various shearing speeds or by the structure of the base.Generally, it appeared that :- The reduction of the overall DOC was higher than 70%, regardless of which type of sand base was used.- In the water coming out of the column made up of round sand, the overall DOC content was without exception lower than 125 mg/L, as would be expected for an infiltration-percolation process.- The treatment of carbon in the columns based on stream sand was in general more effective than that obtained in columns with crushed sand.Concerning the treatment of nitrogen, crushed sand yielded outputs with a reduction in ammonia that was a lot higher than 80% (mean ± SD: 92 ± 4%) and was systematically higher than those obtained with stream sand (mean ± SD: 72 ± 7%). The suspended matter content was extremely low in the effluent; since no suspended matter was introduced into the effluent, the concentration coming out of the column was the direct result of the biofilm becoming detached and/or, to a lesser extent, of the transport of the biomass in the liquid phase. As could be expected, because of the roughness causing more shearing, more particles became detached when the interior solid mass was made up of crushed sand.Using core samples taken from the filter's solid mass, as well as oxygen probes inserted at various levels into the biological engines, we showed that the vertical distribution of the biofilm in the columns, as well as the oxygenation of the porous media during the rest periods, were all correlated with the structure of the solid supports (note that all sands had similar average diameters). Gaseous exchanges within the filter's solid mass were dependent on both the type of coating and the depth at which they took place. The oxygen probes were inserted at depths of 14 cm and 18 cm respectively, to determine the percentage of oxygen saturation in the liquid phase within the filter during one week while the columns were operating. Two phases were characteristic of the exchanges observed in the upper part of the filter's solid mass. First we noted an instantaneous reduction in the oxygen content of the liquid phase, linked to the arrival of a batch, followed by a reoxygenation of this portion. Next there was a long phase, lasting approximately 94% of the time between batches, during which time the oxygen content in the residual moisture remained constant. In the lower part of the solid mass, variation in oxygen content was different. Partial deoxygenation in the liquid phase of the porous media here was primarily due to the biochemical oxidation of the organic matter (i.e., consumption by the biomass). It was also due, to a lesser extent, to the augmentation in moisture content that occurs after each batch, and leads to a reduction in porosity and a decrease in oxygen transfer. During the final phase of drainage, a balance was created between the open porous space with air, and the space containing stagnant moisture. The diffusion of oxygen in the former and its transfer towards the latter thus compensated for this consumption, and it therefore remained constant. If the medium was left to dry out longer, the diffusion and transfer phenomena increased, and we observed an increase in oxygen content.With respect to the vertical distribution of biomass in the columns, we found that it was almost homogeneous inside the stream sand, up to a depth of 28 cm (total depth = 40 cm). Generally, the organic matter content at each point of measurement in the column was higher in the stream sand than in the crushed sand. The variation was greater around 28 cm, where there was a more significant quantity of moisture inside the sand