Modelling analysis of heat transfer in polymeric materials exposed to different heating scenarios

Polymers undergo physical, chemical and structural changes when exposed to heat and/or fire. Thermoplastics melt, decompose and burn; thermosets decompose, char and/or burn, depending on the temperature changes due to external incident heat flux. Detailed in this thesis is a theoretical and numerical heat transfer study, which is undertaken to simulate and experimentally validated temperature variations during melting, decomposition, charring and ignition phases of polymers. For melting, thermoplastic polymers (polypropylene, polyester, polyamide 6, polymethyl methacrylate, polycarbonate and polystyrene) have been used, whereas for decomposition, charring and ignition glass fibre – reinforced epoxy composites have been chosen. For each case a one-dimensional finite difference method, using Matlab as the operator has been developed to determine the transient temperature distributions within the different types of polymers materials. The convective and radiative heat transfer boundary conditions, at the exposed and unexposed sides of polymer samples, have also been taken into account accordingly. While some experimental results to validate the different numerical models built are from other researchers’ work at Bolton, in addition to these, other sets of experiments were specifically developed for this work. The melting behaviour of thermoplastics has been modelled in two scenarios: (i) vertically oriented sample where melt dripping occurs and (ii) horizontally oriented sample within a contained holder in order that the mass will not escape from the containment region. In the the first scenario the sample was placed in a tube furnace, where the radiant heat is uniform on all sides of the sample. This is based on the experimental methodology developed at Bolton University in an earlier project which studied the melt dripping behaviour of polymers. The thermogravimetric and rheological analysis of molten drops had indicated that, depending upon the temperature of the furnace (external heat flux) and the structure of the polymer, in some cases it was pure melting whereas in others it was accompanied by a partial decomposition of the polymer. A one-dimensional finite difference method based on a moving boundary approach has been developed to model the temperatures of the molten drops polymers. The simulated results showed good agreement with the molten drops’ temperatures measured by experiments. In addition, using kinetic parameters, degrees of decomposition in drops obtained at different furnace temperatures were also simulated, which were validated with previous experimental results. For the second scenario, in which the sample is placed horizontally in a container, experiments were conducted using a cone calorimeter with the heat applied only on the top surface, while the other sides of the polymer sample are insulated, A further one-dimensional finite difference method based on a Stefan approach involving phase changing material, has been developed to determine the melting point temperature and to estimate the temperature profile within the polymer slab, to simulate pure melting and melting plus partial decomposition which may or may not catch fire depending upon the degree of decomposition. The predicted results matched well with the experimental results. Furthermore, the heat transfer model was modified to simulate the temperature profiles through the thickness of a glass fibre - reinforced composite exposed to different heat fluxes in a cone calorimeter. This involved incorporating a kinetic model for the decomposition process taking into consideration the varying thermophysical properties as a function of temperature. This is achieved by using the critical heat flux that is the minimum incident heat flux leading to ignition, in the equation defining the ignition temperature, The simulated temperature profiles matched well with the experimental results obtained from previous works at the University of Bolton, giving a much better agreement than previously published models describing this condition. Ignition phenomenon is well described by the model showing a jumping step when the composite polymer ignites and burns. The last part of the work was to simulate the heat transfer in Intumescent coated glass fibre reinforced epoxy composites exposed to heat in a cone calorimeter. On exposure to heat the intumescent coating expands to form a char, the thickness and the thermal conductivity of which, depends on the type of coating. It was not the purpose of this work to model expansion of the coating; rather the emphasis was to understand the thermal barrier efficiency of the expanded char. However, changes to the surface, expansion of the local thickness and char region when exposed to heat were incorporated into the model to gain better agreement with experiment values

Utilisation de l'approche de la déviance positive pour améliorer l'impact d'un programme de supplémentation en fer-folate des femmes enceintes au Sénégal

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Optimisation du blanchiment du tourteau de canola par du peroxide d'hydrogène, extraction des protéines et caractérisation de leurs propriétés fonctionnelles

L'objectif de cette maîtrise était de développer une méthode qui permettra de trouver une formule de blanchiment efficace du tourteau de canola. Dans ce souci d'optimisation, la méthodologie basée sur les surfaces de réponse (MRS) a été utilisée pour déterminer le pH, les concentrations de tourteau de canola (CM) et de peroxyde d'hydrogène (HP) optimums qui procurent le meilleur profil chromatique au produit. La démarche expérimentale consistait à trouver les conditions optimales pour blanchir le tourteau. Nous avons trouvé les réponses suivantes: L*=83,46; a*=-3,66; b*=17,18; BI=18,05, grâce à la combinaison : pH=10, HP=10 (v/v) et CM = 2,65 (p/v). La MSR nous a également permis de trouver une formule de blanchiment qui donne un profil chromatique identique à celui des farines de blé entier pâtissière et tamisée, d'avoine et de seigle. L’autre objectif était d’examiner les conditions d’extraction des isolats de protéines des tourteaux de canola blanchis (ITB) et non blanchis (ITNB) et d’étudier leurs propriétés fonctionnelles; à savoir le pouvoir moussant et émulsifiant qui sont très importants dans des applications alimentaires. L'étude de fonctionnalité des protéines du tourteau blanchi en présence et en absence de sel et leur comparaison avec les protéines du tourteau non blanchi dans les mêmes conditions ont démontré que les ITB ont de bonnes propriétés moussantes et émulsifiantes. Les capacités émulsifiantes des ITB avec ou sans sel sont respectivement 65,22 et 63,83% et restent supérieures à celles des ITNB (50%); les stabilités des émulsions suivent aussi la même tendance. La capacité moussante et la stabilité des mousses des ITNB avec ou sans sel sont inférieures à celles des ITB avec et sans sel. Les résultats ont montré la bonne capacité de l'ITB à former une émulsion et une mousse en présence de sel. Le blanchiment optimal a eu un impact positif sur l'extractabilité de la matière sèche totale et les propriétés fonctionnelles des isolats.The objective of this research study was to develop a method to find a formula for effective bleaching of canola meal. Optimization methodology based on response surfaces (MRS) was used to determine the pH, the concentrations of meal (CM), and hydrogen peroxide (HP) which provide the optimum color profile. The experimental approach was to find the optimum conditions for bleaching canola meal. We found the following parameters: L * = 83.46, a * = -3.66, b * = 17.18, BI = 18.05, with the combination of pH = 10, HP = 10 (v/v) and CM = 2.6515 (p / v). MSR also allowed finding a formula which gives a bleaching color profile identical to whole wheat pastry and sifted flour, oats and rye. The other objective was to analyse/investigate the extraction conditions of protein isolates bleached canola meal (ITB) and unbleached (ITNB) and study their functional properties. The study of protein functionality meal bleached in the presence and absence of salt and their comparison with the unbleached protein meal under the same conditions showed that the ITB have good foaming and emulsifying properties. Emulsifying capacities of ITB with or without salt are 65.22 and 63.83%, respectively, and remain higher than those of ITNB ( 50%); the stabilities of emulsions also follow the same trend. The foaming capacity and foam stability of ITNB with or without salt are lower than those of ITB with and without salt. The results showed good ability of ITB to form an emulsion and foam in the presence of salt. The optimal bleaching had a positive impact on the extractability of dry matter as well as the functional properties of the isolates

Diversité Biologique Et Structure De La Faune Ichtyologique De l’Aire Marine Protégée De Joal-Fadiouth Au Sénégal

Cette étude vise à mieux faire connaître le fonctionnement écologique de l’aire marine protégée (AMP) de Joal-Fadiouth via l’inventaire de sa composition spécifique et la répartition spatiale de sa faune ichtyologique. A cet effet, un suivi bioécologique a été mené durant les 4 saisons hydrologiques de 2015 à 2017, au niveau de 6 stations caractéristiques des habitats de l’AMP, avec les mêmes engins et équipe de pêcheurs. Les analyses statistiques ont été effectuées à l’aide du logiciel XLSTAT 2017. Au bilan, 120 espèces de poissons appartenant à 86 genres et 48 familles ont été identifiées. Les Carangidae sont les plus nombreux avec 13 espèces. Elles sont suivies par les Sparidae (08), les Haemulidae et Mugilidae (07 chacune), les Solidae (06), les Sciaenidae et les Tetraodontidae (05), les Polynemidae et Serranidae (4 chacune), et 6 et 11 autres familles avec respectivement, 3 et 2 espèces. Les 23 autres familles affichent chacune une seule espèce. Seules 2 espèces parmi les 70 jusque-là identifiées par des études antérieures n’ont pas été retrouvées par cette étude qui a permis de revoir cette liste avec 57 nouvelles espèces. Cette richesse spécifique est inégalement répartie dans l’AMP. La station « Kher-ciment » présente la richesse spécifique la plus importante avec 75 espèces, soit 59 % de l’ichtyofaune de l’AMP de Joal-Fadiouth. Elle est suivie de celles du Quai de pêche (70 espèces, 55 %), du Bolong Mbissel et Ngousse Diohé (65 espèces pour chacune, soit 51,18 %), du Bolong Mama Nguedj (64 espèces, 50 %) et de la Zone « tortues » (48 espèces, 38 %). Chacune de ces zones présente une richesse spécifique supérieure au maximum de 52 espèces jusque-là rencontré dans une zone et largement au-delà des 18 espèces d’une station dominante dans l’AMP de Cayar. Avec ces résultats, cette confirme l’importance de ces zones pour le fonctionnement écologique de l’AMP. This study aims to raise awareness of the ecological functioning of the Joal-Fadiouth marine protected area (MPA) through the inventory of its specific composition and the spatial distribution of its ichthyological fauna. To this end, bioecological monitoring was carried out during the 4 hydrological seasons from 2015 to 2017, at 6 stations characteristic of MPA habitats, with the same gear and team of fishermen. The statistical analyzes were performed using the XLSTAT 2017 software. In the balance, 120 species of fishes belonging to 86 genera and 48 families have been identified. The Carangidae are the most numerous with 13 species. They are followed by Sparidae (08), Haemulidae and Mugilidae (07 each), Solidae (06), Sciaenidae and Tetraodontidae (05), Polynemidae and Serranidae (4 each), and 6 and 11 other families with 3 and 2 species respectively. The other 23 families each display a single species. Only 2 of the 70 species so far identified by previous studies were not found by this study, which made it possible to review this list with 57 new species. This specific richness is unevenly distributed in the MPA. The "Kher-cement" station has the highest specific richness with 75 species, or 59% of the ichthyofauna of the Joal-Fadiouth MPA. It is followed by those of the fishing wharf (70 species, 55%), Bolong Mbissel and Ngousse Diohe (65 species for each, or 51.18%), Bolong Mama Nguedj (64 species, 50%) and “Turtles” area (48 species, 38%). Each of these zones has a specific richness greater than the maximum of 52 species hitherto encounted in a station of MPA, and far beyond the 18 species identified in a dominant station in the Cayar MPA. With these results, this study confirm the importance of these zones for the ecological functioning of the MPA

Metallurgical Analysis of Brake Blocks

International audienceThis study focuses on the characterization of train brake blocks. The brake blocks are an essential organ of train speed control system to ensure comfort and safety to passengers and crew. However, poor quality soles can cause a premature wear of the wheels whose consequences are on the one hand, a damaged brake function, and also high repair costs. Samples were carried out on 3 different batches of brake blocks. Their metallurgical characterization consisted of a study of the hardness and microstructural analysis (micro-structures and chemical analyzes) of the different samples. The results show that the hardness of some soles is greater than that of the wheel, mainly associated with a cementite microstructure. This can lead to a premature wear of the wheels at the expense of brake blocks

Analyse de l'expression génique dans les cellules de la granulosa de follicules dominants chez l'espèce bovine

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Exponential behavior of solutions to stochastic integrodifferential equations with distributed delays

In this work, we study the existence, uniqueness, and exponential asymptotic behavior of mild solutions to stochastic integrodifferential delay evolution equations. We assume that the non-delay part generates a C0-semigroup

Asymptotic behavior of neutral stochastic partial functional integro-differential equations driven by a fractional Brownian motion

This paper deals with the existence, uniqueness and asymptotic behavior of mild solutions to neutral stochastic delay functional integro-di erential equations perturbed by a fractional Brownian motion BH, with Hurst parameter H 2 ( 1 2 ; 1). The main tools for the existence of solution is a xed point theorem and the theory of resolvent operators developed in Grimmer [R. Grimmer, Trans. Amer. Math. Soc., 273 (1982), 333{349.], while a Gronwall-type lemma plays the key role for the asymptotic behavior. An example is provided to illustrate the results of this work

Étude comparative des peuplements ichtyologiques de l’Aire Marine Protégée de Joal-Fadiouth et des pêcheries des zones du pourtour non protégées à l’exploitation halieutique

L'effondrement des stocks de poisson est dû à la surexploitation des peuplements ichtyologiques consécutifs aux mauvaises pratiques de pêche au Sénégal. Cette situation a amené les écologistes marins et les gestionnaires de l'environnement à réévaluer les méthodes traditionnelles de gestion des ressources halieutiques. Pour connaitre la dynamique des peuplements ichtyologiques, nous avons mené une étude comparative des peuplements ichtyologiques de l’Aire Marine Protégée de Jaol-Fadiouth et des pêcheries des zones non protégées à l’exploitation halieutique durant la saison froide 2015. Ainsi, l’exploitation des données de pêches expérimentales réalisées au niveau de 16 stations dans les deux zones a permis de faire l’étude. L’analyse des paramètres environnementaux relevés sur chaque station montre que la zone de l’aire marine protégée est similaire à celle des zones non protégées à l’exploitation halieutique. Par conséquent, les éventuelles différences de peuplement ne s'expliquent pas par la variabilité des paramètres physicochimiques. L’analyse de paramètres physico-chimiques, des indicateurs de biodiversité à savoir : la richesse spécifique, les indices de diversité de Shannon-Weaver et d’équitabilité Pielou ont permis de déterminer les caractéristiques environnementales, la composition et la nature des peuplements, d'évaluer l'impact des mesures de gestion des différentes zones.   The collapse of fish stocks is due to the overexploitation of fish populations as a result of poor fishing practices in Senegal. This situation has led marine ecologists and environmental managers to re-evaluate traditional methods of managing fishery resources. In order to know the dynamics of the ichthyological populations, we conducted a comparative study of the ichthyological populations of the Jaol-Fadiouth Marine Protected Area and the fisheries of the areas not protected from fishing during the 2015 cold season. Thus, the exploitation of data from experimental fisheries carried out at 16 stations in the two areas allowed the study to be carried out. The analysis of the environmental parameters recorded at each station shows that the area of the marine protected area is similar to that of the areas not protected from fisheries exploitation. Therefore, any differences in population size cannot be explained by the variability of physico-chemical parameters. The analysis of physico-chemical parameters, biodiversity indicators such as species richness, the Shannon-Weaver diversity index and the Pielou equitability index allowed us to determine the environmental characteristics, the composition and the nature of the populations, and to evaluate the impact of the management measures of the different areas