Renforcement | EPFL Graph Search

En psychologie, le renforcement est un procédé qui augmente la probabilité de répétition d'un comportement. Les théories sur l'apprentissage par renforcement sont étudiées par la psychologie béhavioriste et font l'objet de nombreuses applications visant à modifier les comportements animaux et humains. B.F. Skinner fut le premier à en étudier systématiquement les effets sur des rats et des pigeons. Le renforcement est une procédure par laquelle la fréquence d'apparition d'un comportement va augmenter en fonction de sa conséquence. Le renforcement positif consiste à ajouter un stimulus alors que le renforcement négatif consiste à supprimer un stimulus. L'utilisation des termes "positif" et "négatif" n'ont pas de valeur morale. Les renforçateurs primaires sont des stimuli qui augmentent la probabilité d'une réponse et qui, comme la nourriture, comblent un besoin biologique. Les renforçateurs secondaires sont des stimuli qui augmentent la probabilité d'une réponse et qui, co

Helio-photocatalytic enhancement of the biodegradation of biorecalcitrant pollutants in water

Simeon Kenfack

The importance of the photocatalytic treatment of water is continuously growing since the 80s. In spite of the well management of the existing biological water treatment plants and the constant reinforcement of the wastewater discharge standards, the development of new water depolluting processes among which the photocatalysis is still relevant. It is recognized that certain chemicals mostly from the synthetic chemistry are not or could only be biodegradable under very critical conditions. When these "biorecalcitrant" pollutants are rejected in a biological wastewater treatment plant, they very often cross it without being degraded and thus, they accumulate in the environment and/or in the living beings. Some of them like the phthalates and the pesticides are known for their carcinogenic and mutagen effects or, they induce hormonal disruptions in the animals, including humans. In general, all the Advanced Oxidation Processes (AOP) whose characteristic is to generate hydroxyls radicals (OH) are able to degrade most of the organic molecules including the biorecalcitrant chemicals. As a technology using the photons emitted by a light source to excite a catalyst and facilitate the generation of the 'OH radicals, the photocatalysis would be a more environmental compatible and less expensive process for depolluting such chemicals, if the light source is natural: the sun. For the first time, a study of potential application in the field of helio- photocatalysis was explored in a sub-Saharan Africa country (Burkina Faso), making profitable the significant solar radiation present in that country, to validate certain results obtained using appropriated experimental and analytical methods at the Laboratory for Environmental Biotechnology (LBE) at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. The main objective of this thesis was to contribute to evaluate some physicochemical and technical rules which guide the scaling up processing of the helio-photo-Fenton process. To achieve this, the work was organized in several phases of laboratory work at the EPFL and field apply work at the Ecole Inter-Etats d'Ingénieurs de l'Equipement Rural (EIER) of Ouagadougou in Burkina Faso. To mitigate the deficit of sophisticated analytical material during the field work's periods, a simple analytical method requiring relatively modest equipment was developed and validated in the laboratory and on the field. This thesis is organized in 5 chapters of which the first focuses on the problems of this research and presents the fundamental principles of the photocatalytic processes. Chapter 2 presents the systematic development of a low cost analytical method built up and validated in the laboratory for field's applied studies on three phthalates: the dimethyl phthalate (DMP), the diethyl phthalate (DEP) and the Diallyl phthalate (DAP). The chapter 3 focuses on the study of the optimal parameters influencing the helio-photodegradation of the DEP. In the chapter 4, two case studies on the enhancement of the biodegradability of some biorecalcitrants wastewaters of which, the first evaluates the possibility of integrating the photocatalysis into a global strategy of managing the effluents of a chemical industry and the other treat problem of the depollution of the water polluted by a pesticide are presented. The last chapter presents some modelling approaches allowing to evaluate the solar UVA energy (needed for the helio-photocatalysis) basing on the equation of the solar UVA irradiation which was proposed and tested with the one year solar data of Ouagadougou.

EPFL2006

Stress Fields for the analysis of the faillure load and cracking state of dapped-end beams (Aplicación de modelos de campos de tensiones para el análisis en servicio y rotura de apoyos a media madera)

Miguel Fernández Ruiz, Jaime Mata Falcon, Aurelio Muttoni

The automatic generation of elastic-plastic stress fields (EPSF) for structural concrete members by means of the finite element method has been demonstrated as a suitable approach for the design and assessment of D regions. This methodology allows accounting for an elastic-plastic behaviour of the materials. For concrete, no tensile strength is considered, and the compression softening hypothesis of Vecchio & Collins is incorporated to take into account the effect of the transversal cracking on the compressive strength of concrete. In this paper, the application of this tool for the analysis of the failure load and cracking conditions at serviceability is investigated over a series of experimental tests on dapped-end beams (DEB). The failure of DEB occurred in most cases by spalling of the concrete cover on top of the suspension reinforcement. The models with the EPSF predicted also consistently this failure mode. Contrary to classical approaches of stress fields, where the tensile strength of the concrete cover is neglected (leading thus to conservative estimates of the strength for members failing by cover spalling), it is shown in this paper that EPSF can be suitably adapted to reproduce this failure mode by introducing a fictitious reinforcement in the cover. This reinforcement is introduced to reproduce cover spalling for a critical opening of the spalling cracks developing. With this assumption, a very good estimate of the experimental ultimate loads is consistently obtained, also for prestressed elements and for steel-fibre reinforced members (for which the contribution of the fibres is introduced in the model as an equivalent plastic tensile strength of the concrete). A methodology for the determination of the crack width in the critical regions of DEB for service load levels by using EPSF is also investigated. It is assumed a rigid-plastic approximation for the bond stresses near the crack. The methodology gives also reasonable and consistent estimates of the crack widths for DEB specimens, particularly for those with diagonal reinforcement, in which the cracking process is more stable.

VI Congreso ACHE2014

Helio-photocatalytic enhancement of the biodegradation of biorecalcitrant pollutants in water

Simeon Kenfack

EPFL2006

Miguel Fernández Ruiz, Jaime Mata Falcon, Aurelio Muttoni

VI Congreso ACHE2014