identifier: Lonappan, Linson  (2018). Développement de micro-système imprégné de biocharbon-enzyme (BEMS) pour la dégradation du contaminant émergent – diclofénac.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'eau, 418 p.

subject:
biocharbon-enzyme
microbiochars
contaminants émergents
Diclofénac
traitement des eaux usées

abstract:
Les contaminants émergents attirent de plus en plus l’attention en raison de leur omniprésence dans les milieux naturels, leur impact sur l'environnement ainsi que de leurs effets toxiques sur divers organismes. Le Diclofénac (DCF) est un médicament anti-inflammatoire largement utilisé dans le monde entier. Plusieurs recherches menées au cours des dernières décennies ont confirmé l'ubiquité mondiale de DCF dans l'environnement. Pour le DCF, 30 à 70% sont éliminées par le système de traitement classique dans les stations d'épuration des eaux usées (qui est le principal récepteur primaire du contaminant). Ainsi, le DCF résiduel a été fréquemment détecté dans les eaux douces et connu et sa toxicité a été observée pour plusieurs organismes aquatiques. À titre d’exemple, à une concentration de 1 μg L⁻¹, le DCF induits des altérations physiologiques et cause des dommages aux reins et au foie. Le développement de méthodes de traitement efficace des composés pharmaceutiques est donc nécessaire.
L'identification et la quantification des DCF au Québec au niveau de la station de traitement des eaux usées de la Communauté urbaine (ville de Québec, Canada) est une étape clef pour étudier le devenir du DCF dans l'environnement. A cet effet, un procédé rapide et indépendant de la matrice a été développé en utilisant LDTD-APCI-MS / MS (ionisation chimique à pression atmosphérique désorption thermique diode laser (LDTD-APCI) couplée à une spectrométrie de masse tandem (MS / MS). Le procédé réduit le temps d'analyse par échantillon à 12 secondes comparativement à la méthode conventionnelle LC-ESI-MS / MS qui prend jusqu’à 12 minutes. Les eaux usées non traitées contenaient 64,89 ± 6.7μg L⁻¹ de DCF et l'effluent contenait 15,95 ± 3.7μ g L⁻¹. La quantification du DCF dans les boues des eaux usées a également été réalisée et pour lesquelles, deux méthodes d'extraction ont été étudiées. L’extraction par solvant accélérée (ASE) a été la plus efficace comparée à l’extraction assistée par ultrasons (USE) avec 95,6 ± 7% de récupération. Les boues primaires (1,10 ± 0,15 μg g⁻¹) et boues secondaires (0,90 ± 0,15 μg g⁻¹) contenaient des concentrations importantes de DCF et qui est en outre dirigé vers la sorption du DCF dans les eaux usées. Dans l'ensemble, un enlèvement de près de 76% du DCF a été observé dans la station d'épuration des eaux usées. Cependant, une grande partie de cet enlèvement est due à l’adsorption du contaminant sur les boues des eaux usées. Après avoir déterminé la répartition du DCF tout au long des différentes opérations unitaires de la station d'épuration, il était important de mettre au point des méthodes de traitement.
Le traitement par adsorption a été proposé comme étant un procédé d'élimination efficace de divers contaminants émergents. Dans cette étude, les microparticules de biochars ont été produites à partir du biochar obtenu par broyage et tamisage. Les propriétés du biochar, ainsi que ses capacités d'adsorption sont fortement dépendantes du choix de la matière première agricole utilisée et des conditions de sa production. Les microbiochars ont été caractérisés pour leurs capacités d'adsorption en utilisant le bleu de méthylène comme contaminant organique modèle. Pour le DCF, le microbiochar produit à partir de fumier de porc (BC-PM) a montré d’excellente efficacité d'élimination (99,6%) comparativement à celui obtenu à partir de bois de pin (BC-PW). La diffusion intraparticulaire est considérée l’élément limitant dans le processus d’adsorption. La température, la présence d'ions co-existants, la concentration initiale d'adsorbat et les particules ont joué tous un rôle important dans l'adsorption.
Afin d’améliorer leurs capacités d’adsorption pour le DCF, les microbiochars ont été fonctionnalisées en utilisant divers acides organiques. La fonctionnalisation a augmenté les groupes fonctionnels acides de 23,6%, 10,2% et 26,2%, respectivement pour le bois de pin, le fumier de porc et les microbiochars de coquille d'amande. Les biochars fonctionnalisés à l’acide citrique avaient la capacité la plus élevée pour éliminer le DCF. Pour le biochar à base de bois de pin, l’équilibre est passé de 65 à 80% lors du traitement des eaux contaminées avec le DCF Pour le biochar à base de coquilles d'amande (BC-AS) et dans des conditions similaires, l'efficacité d'élimination de diclofénac est passée de 58 à 84%. Les enzymes lignolytiques, particulièrement la laccase en, a été démontrée efficace pour la dégradation de plusieurs contaminants émergents. Des essais ont été menés pour une production rentable de laccase via l'utilisation des résidus agro-industriels comme substrats. Les résidus d’industrie de jus de fruit (49.16 ± 2,5 U gds ⁻¹) et de l’industrie de pâte et papier (52,4 ± 2,2 U gds⁻¹) se sont avérés être des substrats efficaces comparés aux fibres d’alfa séchées (14,26 ± 0,8 U gds⁻¹). Une dégradation presque totale (99%) a été obtenue après une période de 5 heures lorsque le pH et la température sont fixés respectivement à 4,5 et à 50ºC. L’immobilisation de la laccase sur des supports solides permet d'améliorer sa stabilité et de renforcer le potentiel d'application dans des conditions environnementales réelles. Les procédés d'immobilisation par adsorption et covalente ont été étudiés en utilisant de la laccase brute sur divers microbiochars. Avec tous les types de biochars, et comme l'activité initiale de la laccase est élevée dans la solution brute, l'efficacité de l'immobilisation était élevée aussi. Le modèle qui décrit le mieux à liaison enzymes-micro-biochars est la forme d’une monocouche homogène La laccase immobilisée par des liaisons covalentes a montré une stabilité supérieure à différentes conditions (pH, température et durée de stockage). Avec l'immobilisation covalente de la laccase en utilisant du glutaraldéhyde (5% v / v), le microbiochar à base de lisier de porc a montré l’efficacité d’adsorption la plus élevée (34,1 ± 1. 1 U g⁻¹), suivie par microbiochar de coquille d'amande (25,3 ± 2,8 U g⁻¹) et celui de bois de pin (16,18 ± 0,3 U g⁻¹). En outre, le prétraitement avec de l'acide citrique améliore les interactions de la laccase avec tous les microbiochars et a montré une amélioration particulière de l’ordre de 20% pour le microbiochar à base de coquille d'amandes. À une concentration de 500 μgL⁻¹, l’élimination totale du DCF a été observée avec le complexe micro biochar de lisier de porc-laccase au bout de 3 heures. Plus de 40% de l'activité de la laccase a été maintenue avec tous les systèmes micro-biochars-laccase-après 5 cycles de traitement de DCF d’une durée 6 heures.
Les nouveaux microsystèmes imprégnés biochar-enzyme laccase (BEMS) ont été exploités pour la fabrication d’un bioréacteur à colonne sur lit fixe. Le biochar-la laccase a démontré une efficacité de traitement plus élevé que le biochar brut. De plus, le biochar-laccase a permis une amélioration significative pour le temps de résidence grâce à la biodégradation en parallèle du DCF dans la colonne. Le microsystème biochar imprégné d'enzyme (BEMS) est une approche efficace, durable, verte et rentable pour le traitement des DCF et d'autres contaminants émergents dans divers environnements.

Emerging contaminants are gaining wide attention due to their omnipresence in environmental compartments and their potential environmental as well as toxic effects on various organisms. Diclofenac (DCF) is a prevalent anti-inflammatory drug used throughout the world. Intensive researches carried out in the past few decades have confirmed the global ubiquity of DCF in various environmental compartments. For DCF, about 30–70% removal has been obtained through the conventional treatment system in wastewater treatment plant is the major primary sink. Thus, the untreated DCF has frequent occurrence in freshwater environments and known for its potential toxicity towards several aquatic organisms. At 1 μg L⁻¹, DCF induces physiological alterations and kidney and liver damages in some aquatic organisms and which call up for effective treatment methods for the removal of the pharmaceuticals.
The identification and quantification of DCF in Quebec Urban Community wastewater treatment (Quebec city, Canada) was performed to study the fate of DCF in the environment. For this purpose, a rapid and less matrix-prone method was developed using LDTD-APCI-MS/MS (laser diode thermal desorption-atmospheric pressure chemical ionization (LDTD-APCI) coupled to tandem mass spectrometry (MS/MS). The method reduced the analysis time per sample to 12 seconds when compared with the conventional LC-ESI–MS/MS method (12 minutes). The wastewater influent contained 64.89±6.7μg L−1 of DCF and the effluent contained 15.95±3.7μg L−1. Quantification of DCF in wastewater sludge was also carried out and for the which, two extraction methods were studied. Accelerated solvent extraction (ASE) was found to be effective over ultrasonic-assisted extraction (USE) for the extraction of DCF from wastewater sludge with 95.6 ± 7% recovery. Primary sludge (1.10 ± 0.15 μg g−1) and secondary sludge (0.90 ± 0.15 μg g−1) contained significant amounts of DCF and which further pointed towards the sorption of DCF in wastewater sludge. Overall, nearly 76 % removal of DCF was observed in the wastewater treatment plant; however, a major portion of this was accounted through sorption onto the wastewater sludge. After having determined the partitioning of DCF in different wastewater treatment plant unit operations, it was important to devise treatment methods.
Adsorptive removal has been recognized as an effective removal method for various emerging contaminants. In this study, the micro-biochars were produced from the biochar obtained from pyrolysis reactor outlet through size reduction. Feedstock selection and method of production had significant effects on the biochar properties as well as adsorption capacities. Micro-biochars were characterized for the adsorption experiments using the model organic contaminant methylene blue. For emerging contaminant DCF, Pig manure micro-biochar (BC-PM) showed excellent removal efficiency (99.6%) over pine wood micro-biochar (BC-PW) at 500 μg L⁻¹ of DCF (environmentally significant concentration). Intraparticle diffusion was found to be the major process facilitated the adsorption. Thermodynamics, the presence of co-existing ions, initial adsorbate concentration and particles size played a substantial role in adsorption. Further, the micro-biochars were functionalized using various organic acids for enhanced removal of DCF. The functionalization increased total acidic functional groups by 23.6 %, 10.2 %, and 26.2 %, respectively for pine wood, pig manure, and almond shell micro-biochars. Citric acid functionalized biochars showed the higher removal of the environmentally relevant concentration (500 μg L⁻¹) of emerging contaminant, diclofenac. For pinewood biochar, at equilibrium diclofenac removal increased from 65 to 80 %. For almond shell biochar (BC-AS), under similar conditions, the diclofenac removal efficiency increased from 58 to 84 %.
Ligninolytic enzymes, laccase, in particular, were found to be effective for the degradation of several emerging contaminants. In this study, an attempt has been made for the cost-effective production of laccase through the application of agro-industrial residues as substrates (using Tremetes versicolor (ATCC 20869)). Apple juice industry residue, apple pomace (49.16±2.5 U gds ⁻¹) and pulp and paper solid waste (52.4±2.2 U gds⁻¹) were found to be the efficient substrates for laccase production over dried alfa fibers (14.26±0.8 U gds⁻¹). At environmentally relevant concentrations (500 μg L⁻¹ of DCF), pH of 4.5 and temperature of 50 °C was found to be optimal for the effective degradation of DCF with laccase. Under optimized conditions, up to 99 % degradation was observed for DCF within 5 hours. Immobilization of laccase on solid supports will enhance its stability and further application potential in real environmental conditions. Adsorptive and covalent immobilization methods were studied for the immobilization of crude laccase on various micro-biochars. With all biochars, as the initial activity of laccase increased in the crude solution, the adsorptive immobilization efficiency also increased. Homogeneous monolayer adsorption was found to be the major mechanism of enzyme binding on micro-biochars. Covalently immobilized laccase (using glutaraldehyde as cross linker) showed superior pH, thermal, storage and operational stability. With covalent immobilization of laccase using glutaraldehyde ( 5% w/v), pig manure micro-biochar showed highest laccase binding (34.1±1.1 U g⁻¹) followed by almond shell micro-biochar (25.3±2.8 U g⁻¹) and pine wood micro-biochar (16.18±0.3 U g⁻¹). Further, citric acid pretreatment improved the laccase binding capacity of all the micro-biochars and showed up to 20 % improvement in laccase binding with almond shell micro-biochar. At environmentally relevant concentration (500 μg L⁻¹), the complete removal of DCF was observed with pig manure micro biochar bound laccase within 3 hours under batch mode operating conditions. More than 40 % of the laccase activity was retained with all the laccase-bound micro-biochars after 5 cycles of diclofenac treatment in which each cycle lasted for 6 hours.
Laccase-bound micro-biochars were developed into novel biochar-enzyme impregnated microsystem (BEMS) by developing a fixed-bed column bioreactor. Laccase bound biochar exhibited higher removal efficiency over the raw biochar and significant improvement in breakthrough time was observed which was attributed to the biodegradation of DCF in the column. The biochar-enzyme impregnated microsystem (BEMS) will be promising as an efficient, sustainable, green and cost-effective approach for the treatment of DCF and other emerging contaminants in diverse environments.


identifier: Yellapu, Sravan Kumar  (2018). Développement d'un procédé en aval pour la production de biodiesel en utilisant la biomasse de levure oléagineuse et la boue municipale.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'eau, 298 p.

type:
Thèse
Non évalué par les pairs

subject:
biodiesel
biomasse
levure oléagineuse
boues d'épuration municipale
lipides
glycérol  brut
Yarrowia  lipolytica
Trichosporon  aleaginous

abstract:
La production de biodiesel a attiré l’attention au cours des dernières décennies. Grâce à une réduction des émissions de gaz à effet de serre (GES), les biodiesels peuvent désormais compétitionner avec les sources de carburants à base de pétrole. Actuellement, de manière globale, les usines de production de biodiesel utilisent de l’huile végétale (comestible et non-comestible) et des graisses animales comme matière première. Par contre, ces usines cherchent des alternatives à plus faible coût pour remplacer ces matières.
La production de lipides par des microorganismes oléagineux est une approche intéressante pour les chercheurs et les producteurs de biodiésel. Par contre, la production du biodiésel à partir de lipides demeure économiquement impraticable due au coût élevé de la matière première et des différentes étapes de production telles que la récolte des microorganismes, le séchage de la biomasse, la perturbation des parois cellulaires, l’utilisation de solvants organiques pour l’extraction lipidique, la transestérification et la purification.
Dans cette étude, des matières destinées à l’enfouissement telles que de l’écume (usine d’épuration) et des boues primaires et secondaires ont été étudiées pour en extraire de l’huile. Due à la présence de seulement 30% m/m d’huile dans l’écume, les levures oléagineuses cultivées en présence de glycérol brut (Yarrowia lipolytica et Trichosporon aleaginous) ont été identifiées comme une meilleure alternative puisqu’elles croissent rapidement et qu’elles peuvent atteindre des concentrations de 80 g/L de biomasse avec 50 à 80% m/m de lipides. Par contre, la barrière technologique pour la production de biodiésel à partir de microorganismes oléagineux est le procédé de d’extraction et de purification. Donc, la récolte de biomasse s’est effectuée par la technologie de floculation avec l’utilisation de polymères extracellulaires (PEC) produit par fermentation des biosolides municipaux. Ensuite, une nouvelle approche de perturbation de la membrane cellulaire en milieu humide et de nouveaux solvants tels que le diésel conventionnel ont été étudiés dans le cadre de cette étude. Les lipides ainsi récupérés dans le diésel ont été trans-estérifiés en biodiésel sans évaporation du solvant.
Une recherche rigoureuse a été menée et les matières premières de 3e génération à haut contenu lipidique tel que les levures oléagineuses ont démontré un potentiel intéressant pour une production profitable de biodiésel. Par contre, le procédé d’extraction et de purification demeure le principal défi pour la production de biodiésel à partir de levures. Dans un premier temps, le problème de la récolte des levures a été exploré. Dans cette recherche, un nouveau procédé de récolte de la biomasse oléagineuse (Yarrowia lipolytica) par floculation suivi d’une perturbation des parois cellulaires et de l’extraction des lipides avec du diésel conventionnel comme solvant a été développé. L’alun et le chlorure de calcium comme coagulants avec des PES comme floculant ont été évalués pour la précipitation de biomasse oléagineuse. Les meilleures performances de floculation avec le chlorure de calcium (36 mM) combiné avec des PES (5.85 mg EPS/g biomass) et l’alum (1.2 mM) avec des PES (18 mg PES/g biomasse) ont été de 74.3 % et 79%, avec des vitesses de décantation de 2.93 et 1.46 mm/s, respectivement. La concentration finale de biomasse obtenue dans le précipité était de 166 g/L.
Dans le cadre de cette étude, afin de réduire les coûts du précédé, la perturbation des parois cellulaires a été réalisée sur de la biomasse humide en utilisant une extraction assistée au détergent plutôt que de faire de l’extraction sur de la biomasse sèche comme le procédé conventionnel. La méthode des surfaces de réponse (MSR) a été utilisée pour évaluer l’effet de 3 principaux paramètres (concentration de N-LS, le temps et la température) sur l’efficacité d’extraction (% w/w). Les résultats obtenus à partir de l’analyse statistique indiquent que le model quadratique s’applique dans chacun des cas.
Une récupération maximum de 95.3 ± 0.3% w/w de lipides a été obtenue dans les conditions suivantes : 24.4 mg de N-LS (équivalent à 48 mg N-LS/g biomasse sèche), 8.8 min de traitement, à 30.2°C. L’étude confirme que les le traitement de la biomasse des levures oléagineuses avec le N-LS est une alternative prometteuse pour la perturbation des parois cellulaires.
Par conséquent, une étude plus approfondie a été menée et après perturbation des parois cellulaires à l’aide de N-LS, les lipides libérés en solution ont été directement convertis en biodiesel sans étape de récupération d’huile. De plus, le traitement de la biomasse suivi du traitement par des ultrasons a démontré un rendement maximum d’esters méthyliques d’acide gras (EMAGs) de 94.3 ± 1.9% w/w de lipide en présence de méthanol (ratio molaire méthanol sur lipide de 360:1) et une concentration de catalyseur de 360 mM (64 μL H₂SO₄/g de lipide). La durée de la réaction étant de 5 minutes. Ces résultats ont révélé que les lipides issus des levures oléagineuses peuvent être une bonne alternative pour la production de biodiésel industrielle.
Afin de réduire le coût de production du biodiésel et d’augmenter les crédits de taxes gouvernementaux, des boues municipales secondaires ont été utilisées en amont du procédé pour la production de lipide microbiens. Dans cette étude, de la biomasse de levure oléagineuse (Trichosporon oleaginous) a été cultivée dans des boues municipales et la précipitation de la biomasse à l’aide de PES a été étudiée. La concentration obtenue en solides décantés était de 210 g/L. La biomasse décantée a été traitée avec un traitement séquentiel utilisant le FNA et le N-LS pour perturber la paroi cellulaire. Les lipides microbiens ont été séparés des cellules perturbées en utilisant du chloroforme et du méthanol (1 :1) ou du diésel d’origine pétrolière comme solvant. Les lipides microbiens séparés ont été transestérifiés en biodiésel en conditions ex-situ. Les efficacités maximums d’extraction des lipides de 98.1 ± 1.6 et 95.8 ± 1.1% m/m ont été obtenus en utilisant 75 mg N-LS/g de biomasse, et du chloroforme/méthanol (1 :1) et du diésel comme solvant, respectivement. Dans le cas de l’extraction de lipide assistée avec du FNA, les efficacités maximums d’extraction des lipides de 94.3 ± 1.6 et 90.7 ± 1.1% m/m ont été obtenues avec 40 mg FNA/g de biomasse, et du chloroforme/méthanol (1 :1) et du diésel comme solvant, respectivement. Par contre, durant l’extraction assistée au FNA, l’augmentation de la concentration en FNA au-delà de 10 mg FNA/g de biomasse a affecté le profil des acides gras. Par conséquent, le traitement séquentiel au FNA et au N-LS en utilisant des faibles concentrations de FNA (10 mg FNA/ g de biomasse) suivi par le N-LS (20 mg N-LS/g de biomasse) a été employé et les efficacités maxima d’extraction des lipides de 95.1 et de 92.3% m/m en utilisant l’hexane et le diésel comme solvant, respectivement, ont été obtenues, et ce, sans affecter le profil des acides gras non saturés.
Dans cette étude préliminaire, plusieurs paramètres tels que le volume de solvant, la température, l’agitation et la teneur en eau ont été optimisés pour maximiser l’efficacité d’extraction de l’huile à partir d’écume lyophilisée. L’hexane et le diésel conventionnel ont été comparés pour chaque paramètre afin de déterminer leur efficacité pour l’extraction d’huile. Les paramètres physiques optimaux identifiés pour l’extraction d’huile à partir d’écume lyophilisée sont 75 g de solide/L de solvant à 60°C, sous agitation à 300 rpm pour 30 minutes. Les maximums d’efficacité de récupération obtenus sont de 100% and 94.3% w/w avec l’hexane et le diésel, respectivement. Les paramètres optimaux pour l’écume lyophilisée ont aussi été appliqués pour séparer l’huile à partir des boues primaires et secondaires. Des efficacités de récupération de 95.2% et 94.7% w/w ont été obtenues avec l’hexane et le diésel, respectivement. De plus, la transestérification ex-situ a été réalisée et les résultats ont démontrés que l’écume contient plus de lipides neutres que les boues primaires et secondaires. En bref, l’écume est une matière première potentielle pour la production de biodiésel mais son contenu en huile est de l’ordre de 30% m/m. Le procédé avancé d’extraction de lipides microbiens développé dans le cadre de cette recherche qui utilise les boues municipales et les levures oléagineuses (Yarrowia lipolytica and Trichosporon oleaginous) pourrait permettre d’abaisser les coûts du procédé et rendre le procédé faisable à l’échelle industrielle.

Biodiesel production has received significant attention during the last few decades. Due to a decrease in greenhouse gases emissions (GHG), it has become an efficient approach to compete with that of petroleum-based conventional fuels. Nowadays, world-wide biodiesel industries are using vegetable oil (edible and non-edible) and animal fats for biodiesel production, but they are looking forward towards low-cost feedstocks.
The microbial lipid produced by the oleaginous microorganism is an attractive approach for researchers as well as biodiesel industries. However, biodiesel production from lipids is still not economically feasible due to high feedstock cost and multiple steps involved in downstream processing such as biomass harvesting, biomass drying, cell wall disruption, microbial lipid extraction using organic solvent, transesterification and biodiesel purification.
In this study, diverted waste feedstocks such as scum, primary and secondary sludge were investigated for oil extraction. Due to the presence of less than 30% w/w oil content in scum, an alternative feedstock such as oleaginous yeast grown in crude glycerol medium (Yarrowia lipolytica and Trichosporon oleaginous) was identified, which grow rapidly and produce up to 80g/L biomass with 50 - 80% w/w lipid content. However, the bottleneck for biodiesel production using microbial lipid bearing biomass is downstream processing. Therefore, biomass harvesting was done by flocculation technology with extra polymeric substances (EPS) produced using waste water sludge. Furthermore, a cell wall disruption approach using wet biomass for cell wall disruption and novel solvent such as petroleum diesel were investigated in this study to recover lipids. The recovered lipids present in petroleum diesel were further transesterified to biodiesel without solvent drying.
A rigorous research was conducted and high lipid containing 3rd generation feedstock such as microbial oil from oleaginous yeast was found to be proficient for biodiesel production. However, downstream processing is a massive challenge for oleaginous yeast biomass and the preliminary step was biomass harvesting without centrifugation.
In this research, a new process of harvesting the oleaginous yeast biomass (Yarrowia lipolytica) by flocculation followed by cell wall disruption and lipid extraction with petroleum diesel as a solvent was developed. Alum and calcium chloride along with EPS as a flocculant were evaluated for lipid bearing biomass settling. The maximum flocculation activity of biomass using calcium chloride (36 mM) in combination with EPS (5.85 mg EPS/g biomass) or Alum (1.2mM) with EPS (18 mg EPS/g biomass) was 74.3 and 79 % and the settling velocity was 2.93 and 1.46 mm/s, respectively. The final settled biomass concentration obtained was 166g/L.
In this study, in order to reduce the process costs, the cell wall disruption was performed on wet biomass using detergent assisted lipids extraction as opposed to the conventional process that uses dry biomass. Response surface methodology (RSM) was used to investigate the effect of three principle parameters [N-lauroyl sarcosine (N-LS) concentration, time and temperature] on microbial lipid extraction efficiency (% w/w). The results obtained by statistical analysis showed that the quadratic model fits in all cases. Maximum lipid recovery of 95.3 ± 0.3 % w/w was obtained at the optimum level in the following conditions of process variables [N-LS concentration 24.42 mg (equal to 48 mg N-LS/g dry biomass), treatment time 8.8 min and reaction temperature 30.2 oC. The study confirmed that oleaginous yeast biomass treatment with N-LS would be a promising approach for cell wall disruption.
Hence, further study was conducted and after N-LS assisted cell wall disruption, the lipid in solution was directly converted to biodiesel without oil recovery. Moreover, The N-LS treatment of biomass followed with ultrasonication revealed maximum Fatty acid methyl esters (FAMEs) yield of 94.3 ± 1.9 % w/w using methanol to lipid molar ratio 360:1 and catalyst concentration 360 mM (64 μL H₂SO₄/g lipid) within 5 minutes reaction time. These results revealed that the microbial lipid from oleaginous yeast can be good alternation for industrial biodiesel production.
To decrease the cost of biodiesel production and for tax credits, in upstream processing, municipal secondary wastewater sludge was used for microbial lipid production. In this study, oleaginous yeast biomass (Trichosporon oleaginous) was cultivated in a municipal wastewater sludge and develped biomass settling method usig EPS was investigated . The obtained concentration of settled solids was 210 g/L after biomass settling. The settled sludge biomass was treated with sequential treatment using (FNA) Free nitrous acid and N-LS to disrupt cell wall. The microbial lipid was separated from the disrupted cells using chloroform and methanol (1:1) or petroleum diesel as solvent. The separated microbial lipid was ex-situ trans esterified to biodiesel. The maximum lipid extraction efficiencies of 98.1± 1.6 and 95.8 ± 1.1% w/w were achieved using 75 mg N-LS/g of biomass, and chloroform/methanol (1:1) and petroleum diesel as solvent, respectively. In case of FNA assisted lipid extraction, the maximum lipid extraction efficiencies of 94.3 ± 1.6 and 90.7 ± 1.1 %w/w were obtained at 40 mg FNA/g biomass using chloroform and methanol (1:1) and petroleum diesel as a solvent, respectively. However, during FNA assisted lipid extraction, increase in FNA concentration beyond 10 mg FNA/g biomass, affected the fatty acid profile. Therefore, sequential FNA and N-LS treatment using low concentration of FNA (10 mg FNA/g biomass) followed by N-LS (20 mg N-LS /g biomass) was employed and maximum lipid extraction efficiency of 95.1 and 92.3% w/w using hexane and petroleum diesel was obtained without any effect on unsaturated fatty acids profile.
Low cost feedstock such as primary, secondary sludge and scum obtained from the municipal wastewater treatment plant for biodiesel production were investigated. Various parameters such as solvent volume, temperature, agitation and moisture content were optimized to maximize the oil extraction efficiency using freeze-dried scum. The oil extraction efficiency was compared for each parameter using hexane and petroleum diesel as a solvent. The optimum physical parameters for oil extraction using freeze-dried scum were 75 g solids/L solvent, temperature 60oC, agitation 300 rpm for 30 min and maximum oil extraction efficiency of 100 and 94.3% w/w were obtained using hexane and petroleum diesel respectively. The optimized parameters for freeze-dried scum were further used to separate oil from dried primary and secondary sludge and oil extraction efficiency of 95.2 and 94.7 % w/w was obtained using hexane and petroleum diesel respectively. Furthermore, the ex-situ transesterification was performed, and results showed that scum had a higher content of neutral lipid than that of primary and secondary sludge. In brief, scum is a potential feedstock for the production of biodiesel but the oil content in scum is ≤ 30% w/w.
The advanced downstream process for lipid extraction from oleaginous biomass and municipal sludge (scum) followed by lipid conversion to biodiesel developed during this research will make biodiesel production feasible at industrial scale.


identifier: Blanchette, Marianne  (2018). Services hydrologiques rendus par les milieux humides dans un contexte dynamique d'occupation du territoire : étude de cas du bassin versant de la rivière Saint-Charles.  Mémoire.  Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en sciences de l'eau, 130 p.

subject:
bassin versant
rivière Saint-Charles
Ville de Québec
hydrologie
gestion du territoire
services écologiques
activités  anthropiques
milieux humides

abstract:
Le développement anthropique (urbanisation, agriculture, exploitation forestière, etc.) a un impact sur l’environnement et ses différents écosystèmes. Les milieux humides (marais, marécages, tourbières) d’un territoire procurent des services écologiques qui contribuent à restreindre l’impact négatif de ces activités sur certaines composantes naturelles. Or, les activités anthropiques affectent également les milieux humides, entre autres par l’empiétement sur leur superficie et par la modification de leur aire d’alimentation en eau. De cette manière, on assiste depuis le dernier siècle, à une diminution des superficies occupées par les milieux humides et on peut penser que cette perte a un impact, à son tour, sur les services écologiques fournis par ces écosystèmes. Au sein des services écologiques que l’on attribue aux milieux humides, on distingue les services hydrologiques, dont l’atténuation des crues, le maintien des débits en période d’étiage, la recharge de l’eau souterraine et l’amélioration de la qualité de l’eau.
L’objectif principal de ce projet est de quantifier l’impact de l’évolution des superficies occupées par les milieux humides sur deux des services hydrologiques rendus par ceux-ci, soient l’atténuation des crues et le support aux étiages, à travers une étude de cas appliquée au bassin versant de la rivière Saint-Charles, Québec, Canada. Les connaissances actuelles portent à croire qu’une diminution des superficies de milieux humides augmenterait la vulnérabilité du bassin versant face à ces événements hydrologiques.
Afin d’explorer cette hypothèse, une méthode combinant l’utilisation des systèmes d’information géographiques et de techniques issues de la télédétection et de la modélisation hydrologique a été développée. Ainsi, dans le cadre d’une première étape, des scénarios d’occupation du sol, incluant la répartition des milieux humides, ont été générés à partir d’images d’archives Landsat pour les années 1978, 1985, 1992, 2001 et 2014. Ces scénarios ont été produits à l’aide d’une méthode novatrice de classification orientée-objet bonifiée par les résultats d‘une étude des caractéristiques géomorphologiques associées aux milieux humides. Ils ont ensuite été intégrés dans la plateforme de modélisation hydrologique PHYSITEL/HYDROTEL afin de simuler pour chacun, les débits à différents points d’intérêts, avec et sans la prise en compte des milieux humides.
L’analyse des caractéristiques géomorphologiques a permis d’identifier deux jeux de données pour la détection des milieux humides, soient la forme des versants hôtes (formes de Dikau) et les classes de drainage des sols. La méthode de classification d’images utilisée a permis d’atteindre une précision de 80 à 81% pour les scénarios de 2014, comparativement à 60 et 66% pour les classifications réalisées sans l’utilisation des données géomorphologiques secondaires. Les scénarios témoignent d’une modification importante du territoire entre 1978 et 2014, incluant une diminution relative des superficies de milieux humides de 8 à 53 % de même qu’une augmentation du territoire urbain parallèlement à une diminution des activités agricoles. Les résultats de simulations sont également conformes aux résultats escomptés et indiquent que l’impact des milieux humides sur les débits de crues et d’étiage est généralement cohérent avec l’évolution de leur superficie à l’échelle des sous-bassins versants, soit : (i) une augmentation des milieux humides se traduisant par une augmentation de leurs services hydrologiques ou, inversement, (ii) une diminution des superficies de milieux humides ayant pour conséquence une diminution de ceux-ci.
Les conclusions de cette étude mettent de l’avant le rôle favorable des milieux humides dans l’atténuation des crues et le maintien des débits en période d’étiage, de même que la perte des services hydrologiques qui accompagne la diminution des superficies associées à ces écosystèmes. Les travaux réalisés dans le cadre de ce mémoire ouvrent la porte vers de nouvelles orientations de recherche. Des données issues de relevés LiDAR permettront d’affiner l’étude des caractéristiques géomorphologiques associées aux milieux humides et pourront également être intégrées directement dans la plateforme de modélisation sous forme d’un modèle numérique d’élévation, ce qui augmentera la résolution à laquelle les différents phénomènes hydrologiques y sont simulés. L’ajout de services hydrologiques supplémentaires associés aux milieux humides, tels que l’amélioration de la qualité de l’eau par la rétention des matières en suspension, pourrait également faire l’objet de travaux ultérieurs. Ces nouvelles avenues permettront de mieux comprendre le rôle des milieux humides et de mieux cibler les réseaux de conservation en vue de maintenir les services hydrologiques qui leur sont associés.


identifier: Almesrati, Ali  (2018). Comparative study based on first principles to investigate unstrained and epitaxially strained Bi₂FeCrO₆ properties.  Mémoire.  Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en sciences de l'énergie et des matériaux, 102 p.

subject:
unstrained multiferroic Bi2FeCrO6(BFCO)
BFCO epitaxially strained
SrTiO3(STO) substrate
electronic and magnetic properties

abstract:
Using density functional theory, we have performed a comparative study between unstrained multiferroic Bi₂FeCrO₆ (BFCO) and BFCO epitaxially strained on SrTiO₃ (STO) substrate. We have compared the predicted structural, magnetic, and electric properties in order to understand the effect of epitaxial strain. In this work, all calculations were performed using the LSDA+U formalism implemented in the VASP code and used a 8×8×8 Monkhorst-Pack grid of k- points and a cutoff energy of 500 eV.
We have first investigated the properties of the unstrained system that has a rhombohedral symmetry and belongs to the R3 space group, with lattice parameters arh=5.47Å and αrh=60.09°. The lattice parameters of the BFCO unit cell obtained through spin-polarized calculations and complete relaxation. The results revealed small differences with what has been reported in literature. The differences are chiefly in the contribution of Fe and Cr to the total magnetic moment, the energy of the fully optimized structure, as well as the position of some ions. The total magnetic moment per unit cell of the ferrimagnetic high spin (FiMHS) and ferromagnetic high spin (FMHS) configurations are 1.987 μB and 7.66 μB, respectively, while that of the ferrimagnetic low spin (FiMLS) and ferromagnetic low spin (FMLS) configurations results in values of 3.8 μB and 1.88 μB, respectively. For completeness, the ionic charges, as well as the density of state have been calculated. Despite slight differences, our results are in overall agreement with what has been reported in the literature.
Secondly, we have investigated the effect of the epitaxial strain on the electronic and magnetic properties of the BFCO system. To this end, the lattice parameters of the rhombohedral BFCO unit cell have been fixed to the STO parameters in the plane of the BFCO/STO interface and the out-of-plane lattice parameter has been varied. We found that FiMHS remains the ground state configuration of the BFCO system under the epitaxial constraint of STO. The influence of the epitaxial deformation imposed by the STO substrate mainly manifests itself in the ionic contribution to spontaneous polarization by inducing a change of 7.64 μC cm⁻² for the the ground state (FiMHS), and producing a total polarization estimated at 90.24 μC cm⁻², as compared to 79.24 μC cm⁻² in the unstrained case. The magnetic moments of the constrained and unconstrained BFCO are very similar, the main difference being observed for the FiMLS phase, with 1.905 μB instead of 1.880 μB. Finally, we have calculated the density of states. Comparing with the case of the system without constraint, we found that the band gap remains practically unchanged for FiMHS, is reduced by 0.1 eV (-10%) for FMHS, and almost vanishes for FMLS and FiMLS.


identifier: Benahmed, Yacine  (2018). Analyse sémantique pour systèmes de dialogue verbaux.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en télécommunications, 231 p.

subject: modèles de langage

subject: ontologies

subject: n-grammes

subject: reconnaissance automatique de la parole

subject: algorithmes évolutionnaires

subject: language models

subject: ontologies

subject: n-grams

subject: automatic speech recognition

subject: evolutionary algorithms

abstract:
Les modèles de langages statistiques font partie intégrante de nombreuses applications telles que la reconnaissance automatique de la parole, la reconnaissance automatique de l’écriture, la saisie prédictive, la traduction automatique du langage, etc. Malgré les développements récents dans le domaine des réseaux de neurones profonds, les N-grammes demeurent tout de même pertinentes dans des domaines où les ressource linguistiques ou computationnelles sont limitées. L’objectif de cette thèse est de présenter un nouvel algorithme de lissage des N-grammes utilisant l’information sémantique lattente aux ontologies. Comme le langage offre une très grande flexibilité dans sa façon d’exprimer une idée, nous utiliserons les relations sémantiques entre les N-grammes observées et les N-grammes non-observées afin d’estimer les probabilités d’observation de ces dernières dans de nouvelles conditions. Nos résultats démontrent qu’il est possible d’obtenir une réduction de 0,93 bit de l’entropie du modèle de langage. Par ailleurs, afin d’optimiser ces modèles de langages, nous proposons d’évaluer la performance de divers algorithmes évolutionnaires. Nos résultats montrent que l’optimisation par algorithmes génétiques permet de couvrir une plus grande partie de l’espace de recherche, au coût d’une plus grande variance dans la solution obtenue. Pour sa part, l’optimisation par essaims particulaires fait preuve d’une moins grande variance dans les solutions obtenues, tout en demeurant aussi performante que l’optimisation par algorithme

 language models are an integral part of many applications such as automatic speech recognition, automatic recognition of writing, predictive input, automatic translation of the language, and so on. Despite recent developments in the field of deep neural networks, N-grams remain relevant in areas where linguistic or computational resources are limited. The objective of this thesis is to present a new algorithm of smoothing N-grams using the semantic information latent to the ontologies. Since language offers a very high degree of flexibility in the way it expresses an idea, we will use the semantic relations between the observed N-grams and the non-observed N-grams in order to estimate the observation probabilities of the observed N-grams in new conditions. Our results show that it is possible to obtain a 0.93 bit reduction of the entropy of the language model. Moreover, in order to optimize these language models, we propose to evaluate the performance of various evolutionary algorithms. Our results show that optimization by genetic algorithms makes it possible to cover a larger part of the research space at the cost of a greater variance in the solution obtained. For its part, the optimization by particulate swarms shows less variance in the solutions obtained, while remaining as efficient as the optimization by genetic algorithm.


identifier: Chakrabartty, Joyprokash  (2018). Oxide perovskites for solar energy conversion.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 221 p.

subject:
solar energy
perovskite materials

abstract:
Inorganic ABO3 perovskite materials exhibit exotic physical and chemical properties due to their exceptional crystal structures and thus offer exciting opportunities for spintronics, computer memories, sensors, microwave and photovoltaic (PV) device applications. Since the discovery of bulk photovoltaic (BPV) effect in non-centrosymmetric crystals, the perovskite oxides including BaTiO₃ (BTO), LiNbO₃ (LNO), BiFeO₃ (BFO), BiMnO₃ (BMO), and Pb(Zr,Ti)O₃ (PZT) drew enormous interest in fundamental science research, as they exhibit either a suitable band gap or larger than band gap photovoltages (up to 1000 V) under homogeneous light illumination. However, owing to their insulating characteristics retain even at the dimensions down to nanometer scale, the charge carrier conduction in polar perovskites is extremely poor resulting in the generation of low photocurrent density, typically in the μA/cm² range and below. Driven by the challenges of improving photocurrent density, in this project, we have investigated BMO and BFO compounds in view of their integration as active materials in PV devices in order to improve the photocurrent density and thus solar power conversion efficiency (PCE). BMO in thin film form possesses ferroelectric behavior i.e. a remnant polarization of ~6 μC/cm² at room temperature and its low band gap value (~1.2 eV) efficiently absorbs light wavelengths exceeding the visible wavelengths of the solar spectrum. In contrast, BFO thin films exhibit strong ferroelectricity with a remnant polarization of ~ 55 μC/cm² and a band gap of ~2.7 eV that corresponds to visible light of solar spectrum. Although the physical and chemical properties of various forms of BFO, from bulk to nanoparticles are widely investigated in solar cells, the potential of BMO alone or in combination with other perovskites is rarely investigated and reported so far in the field of solar energy conversion. In the first part of this thesis, we demonstrate a bilayer-stacking scheme, more specifically a heterostructure based on BFO/BMO epitaxial bilayer thin films grown by pulsed laser deposition (PLD) onto Niobium doped (111)-oriented SrTiO₃ (STO) substrates. The BFO/BMO bilayers as photoactive materials in solid-state PV devices show remarkable PCEs up to 1.43% under 1 sun solar radiation (AM 1.5G), which is higher than those reported values for individual BFO or BMO thin films. The fill factor (FF) is determined to be 0.72 which is a remarkable value for ferroelectric perovskite-based devices. The bilayers exhibit prominent ferroelectric behavior (~100 μC/cm²) compared to individual BFO or BMO films. To describe the PV responses, we use a traditional interfacial model where an interface generated electric field is significantly modulated by spontaneous polarization of the materials.
In the second part, we demonstrate a PV device based on Bi-Mn-O composite thin films which exhibits a PCE of 4.20%. The composite materials are made of two different types of crystal phases: BMO and BiMn₂O₅. The former is ferroelectric with a band gap of ~1.20 eV as specified previously, while BiMn₂O₅ is semiconducting with a band gap of ~1.23 eV. The composite films are grown by PLD on (100) oriented Niobium doped STO single crystal substrates. The crystal structure of both phases in the composite films is characterized by transmission electron microscopy (TEM) and further confirmed by Raman spectroscopy (RS) analysis. Conductive atomic force microscopy (C-AFM) and Kelvin probe force microscopy (KPFM) under illumination show the increased photocurrent and photovoltage generations across BMO /BiMn₂O₅ grain boundaries (GB) compared to the interior of the grains. The ferroelectricity of BMO does not play a significant role in the PV effect, as confirmed by combined Piezoresponse force microscopy (PFM) and KPFM measurements. The results are described in the framework of GB barrier potentials. In the last part, we describe the photocatalytic properties of BMO thin films and nanostructures, both grown epitaxially on (111) oriented Niobium doped STO substrates by PLD. The nanostructures were achieved using nanostencils i.e. shadow masks with a periodic array of nanometer-scale circular features. Photoelectrochemical properties of films and nanostructures as working electrodes are investigated by linear sweep voltammetry (LSV) measurements under chopped illumination. The nanostructures exhibit photocurrent density of ~0.9 mA/cm² at 0.8 V vs Ag/AgCl (1.38 V vs reverse hydrogen electrode (RHE)) which is substantially higher than the values recorded in thin films, ~10 μA/cm² at 0.4 V vs Ag/AgCl (0.98 V vs RHE) under 1 Sun radiation. Band alignments with respect to the redox potential of water and gas chromatograph measurements demonstrate that the BMO photoelectrodes (both films and nanostructures) are suitable for oxygen evolution reactions.


identifier: Cui, Daling  (2018). The investigations of host/guest structures based on covalent organic frameworks at solution/solid interfaces.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 192 p.

subject:
Molecular self-assembly on 2D surfaces
Covalent Organic Frameworks
COF
development of H/G structures
STM

abstract:
Covalent organic frameworks (COFs) have gained significant attention in many
applications due to their porous crystalline structures with high architectural and
chemical robustness and customized topologies. A high-quality extended
two-dimensional (2D) hexagonal porous COF-1 network can be obtained through
cyclocondensation of three 1,4-benzenediboronic acid (BDBA) monomers by using
excess water as the chemical-equilibrium-manipulating agent on a highly oriented
pyrolytic graphite (HOPG) substrate. The surface-confined COF-1 can be used as
template to recognize different guest molecules, allowing formation of a host/guest
(H/G) structure. The intrinsic features of H/G structures lead to their wide
applications in molecular recognition, catalysis, gas storage, separation and directed
crystallization. Driven by the potential applications, the present work in this thesis
concentrates on the preparation and properties of H/G structures based on COF-1
templates at the solution/solid interface.
Firstly, scanning tunneling microscopy (STM) images show that the surface-supported
two-dimensional COF-1 can act as a host architecture for C60 fullerene molecules,
predictably trapping the molecules under a range of conditions. C60 adsorbs in the
COF-1 template in two different sites, the top-site (T) and the pore-site (P). The
fullerenes occupy the COF-1 lattice at the heptanoic acid/HOPG interface, and in
dried films of the COF-1/fullerene network that can be synthesized through either drop-deposition of fullerene solution or by a dipstick-type synthesis in which the
surface-supported COF-1 is briefly dipped into the fullerene solution.
COF-1 can be synthesized from different solvents. When 1,2,4-trichlorobeznene
(TCB) is used, STM images reveal the adsorption of TCB in the hexagonal pore of
COF-1 template at TCB/HOPG interface. A well-defined loop boundary formed by a
chain of pentagonal and heptagonal pores allowed us to investigate the effect of pore
shape and size on TCB adsorption, suggesting that both geometrical and size effects
are important in binding the TCB. When both C60 and TCB are present at the
TCB/HOPG interface, TCB molecules are selectively trapped in the pore-site,
whereas fullerenes adsorb on the top-site of COF-1. While the former structure is
stabilized by Cl…H hydrogen bonds, the latter is controlled by van der Waals (vdW)
interactions. These results suggest that surface-supported 2D porous COFs can
selectively bind different molecules at specific sites via different types of interactions
and COFs may offer a powerful platform for the recognition and patterning of guest
molecules.
Moreover, a 2D COF-1 can template solution-processed C60 guest molecules to form
several solvent-dependent structural arrangements and morphologies via a 2D to 3D
growth process. When TCB is used as solvent, C60 molecules form a template-defined
close packed structure. When heptanoic acid is used as solvent, a range of lower
density architectures that deviate from the template-defined close packing are
observed. This difference is attributed to the co-adsorption of the heptanoic acid solvent molecules, which is only achieved in the presence of the template. This work
demonstrates the possibility to precisely control molecular self-assembly to form
designed 3-dimensional (3D) structures through the synergistic combination of
template and solvent effects.


identifier: Hidalgo-Aguire, Maribel  (2018). Investigation of pulsatile retinal deformation as new biomechanical descriptor of the human ocular dynamics for glaucoma prognosis.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 176 p.

subject:
optic nerve head
glaucoma
image processing
optical
coherence tomography
ocular biomechanics
ocular dynamics
retinal
deformation

abstract:
Glaucoma is the second leading cause of blindness worldwide. The facts
that glaucoma does not present any symptoms until major visual loss has
occurred and that the primary causes of this neuropathy remain unknown
make it challenging for both, diagnosis and treatment. While elevated
intraocular pressure (IOP) remains the primary risk factor, other parameters
such as low ocular perfusion pressure, ocular blood flow and the
elasticity of the sclera and lamina cribrosa have been identified in the last
years as additional factors potentially influencing the risk, prevalence and
progression of the glaucomatous neuropathy.
Theoretically, an individual’s susceptibility to IOP is in part determined
by the eye geometry and tissue anatomy, therefore, it seems natural to
consider biomechanics as framework for explaining how IOP-related stress
and strain influence the physiology and pathophysiology of the connective,
neural and vascular tissue, causing the changes on the structural and
functional integrity of the optic nerve observed in glaucoma. The key
challenge is then to understand how ocular biomechanics, in combination
with the aforementioned risk factors, are transduced into tissue damage.
It has been demonstrated that glaucoma is directly related with blood
flow deficiencies in the retinal and choroidal circulation. The choroid has
the highest blood flow per gram tissue of any organ in the human body
and this flow is 80 % pulsatile. This pulsatility has been hypothesized to
drive the retina forward while expanding the sclera, leading to a pulsatile
deformation of the axons traveling from the retina and through the lamina
cribrosa to the brain. If we consider that the mechanical properties of the
tissues are also altered during the progression of the disease, then is very
likely that such deformation may change. Within this framework, the present work is centered on the study and characterization
of the peripapillary retinal tissue deformation due to choroidal
vascular pulsatility and its possible implication in axonal damage and loss
of the retinal nerve fiber layer in glaucoma. The general strategy designed
to perform such investigation is to use video rate optical coherence tomography
images of the optic nerve head combined with fully automated
image analysis algorithms specially developed to measure and determine
retinal deformation. A cross-sectional study was then carried out at the
ophthalmology clinic of the Maisonneuve-Rosemont Hospital to evaluate
peripapillary retinal deformation on patients that cover the most representative
part of the glaucoma spectrum.
The obtained results show that healthy eyes have significantly larger deformation
of the peripapillary retina compared with the glaucoma spectrum.
The measured deformation correlates differently with the principal risk
factors of the glaucomatous neuropathy depending on diagnosis. Reduced
retinal displacement proved to be related to glaucoma progression predictors
showing that the biomechanical properties of the eye are altered even
when there is no evident changes in the optic nerve head structure.
Due to the versatility of the segmentation algorithm, it was possible to
carry out a preliminary study to investigate retinal deformation around
the macula using images previously acquired from a different clinic study.
In this case, perifoveal retinal deformation in healthy eyes resulted to be
significantly larger than in early glaucoma. Furthermore, ocular rigidity
as well as changes in ocular volume were correlated with perifoveal retinal
displacement in healthy eyes, which confirms that the observed deformation
is driven by choroidal pulsatility.
All these results suggest that the amount of retinal deformation should be
further investigated since it could be potentially used as a new biomechanical
descriptor of the eye for early diagnosis and assessment of glaucoma
progression.


identifier: Beaulieu, Samuel  (2018). Probing femtosecond and attosecond electronic and chiral dynamics: high-order harmonic generation, XUV free induction decay, photoelectron spectroscopy and coulomb explosion.  Thèse.  Bordeaux - Québec, Université de Bordeaux - Université du Québec, Institut national de la recherche scientifique, Doctorat des Sciences Physiques et le l'Ingénieur, Spécialité Lasers, Matière et Nanosciences, 296 p.

subject:
laser
génération d'harmoniques
spectroscopie


identifier: Huang, Wei  (2018). Transparent conducting oxides and multiferroic perovskites for solar energy conversion applications.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 176 p.

subject:
solar energy
photovoltaic cells

abstract:
Clean and sustainable solar energy is regarded as one of the most reliable and abundant energy sources to replace fossil fuels. To harvest this energy, in the past several decades, the research trend has been towards exploring novel materials and photon-to-electron mechanisms to achieve higher efficiency in solar energy conversion applications, such as photovoltaic (PV) cells. The PV effect is used to directly harvest solar energy by converting the incident photons into following free charge carriers and thus produce electricity. The emerging PV cells mainly differ in how they operate in practice, that is, in the mechanisms that make the sequence of the generation, separation and transport of electronic charge carriers possible. Elucidating those mechanisms is of fundamental importance for understanding the working principle of each solar cell type, and for its further performance optimization. In conventional p-n junction based PV cells, the charge separation is determined by the existence of a gradient in the electrochemical potential, also known as intrinsic built-in electric fields. Moreover, solar-driven water splitting and hydrogen generation technologies that produce hydrogen (H₂ gas) and oxygen (O₂ gas) by directly decomposing water using an artificial photocatalytic electrode have been extensively studied as a fundamental technology for the future, due to its simplicity, low-cost operation and the use of nearly neutral pH water, such as seawater for large scale solar-fuel production. In the semiconductor photocatalysts, the carrier extraction is no longer limited by thermodynamic diffusion, but the transport of spatially separated electron-hole pairs to the photocatalyst surface is determined by the surface band bending. Ferroelectric (FE) oxides have recently emerged as a new alternative pathway to achieve the separation of photo-generated charge carriers, and their application in photon-to-current (e.g., PV cells, photodetectors) and photoelectrochemical (PEC) devices was recently started to be explored. Since the discovery of PV effect in these materials over 50 years ago, ferroelectric devices including solar cells (FESC) and PEC cells have attracted significant attention owing to many unique advantages. This technology involves a simplified structure and fabrication methods as well as stable and abundant materials. Different from the p-n diode or Schottky diode solar cells, in the FESC, FE polarization plays a dominant role in charge separation and transport. FESC provides reversible directions of photocurrent and photovoltage by polarization direction switching, and also generates above bandgap open-circuit voltages (Voc up to 40 V), which potentially permit to surpass the Shockley-Queisser limit observed in traditional semiconductors cells.
While for a long time such devices were characterized by weak performance values, recent advances led to significant breakthroughs by using multiferroic materials. Multiferroics combine two ferroic functionalities (specifically FE, ferromagnetic or ferroelastic), and typically possess a magnetic order parameter besides the FE one and the electron-electron interaction regulating the magnetic ordering induced a smaller gap (e.g., 2.6–2.7 eV for BiFeO₃ and 1.4–2.4 eV for Bi₂FeCrO₆) than other FE materials (e.g., 3.2–3.6 eV for La–doped Pb(Zr,Ti)O₃ and 3.2 eV for BaTiO₃). Among these multiferroics, double-perovskite Bi₂FeCrO₆ (BFCO) is highly promising in PV and photocatalytic applications due to its nontoxicity, chemical stability, narrow bandgap, huge light absorption coefficient (2.5 × 10⁵ cm⁻¹), large remnant polarization (55 μC cm⁻² at room temperature (RT)) and magnetization (160 emu cm⁻³).
A breakthrough in the field of PV and PEC devices occurred through our recent study on multiferroic BFCO epitaxial thin films, which demonstrated a high efficiency solar energy conversion (solar to electrical or chemical energy). In such material, lower band gap and large FE polarization promote an effective charge carrier generation and separation. Single crystalline BFCO with higher ratio of Fe/Cr cation ordering (R≈0.5−5.1%) showed a lower bandgap (Eg≈1.4−1.8 eV) accompanied with weak FE polarization (P≈5−20 μC cm⁻²), which exhibit thus a semiconductor behavior. In despite of a larger absorption of sun light by semiconducting BFCO films, the weak FE polarization induced internal electric field decreases the separation power of photogenerated carriers and increases the recombination loss. This dramatically affects the performance of the devices. These results clearly suggest a relationship between the optical property, ferroelectricity and crystal structure of BFCO thin films. To advantageously exploit the semiconducting properties of BFCO for PV application, the p-i-n device architectures have to be designed and developed. Here, an intrinsic semiconductor is sandwiched between a heavily doped p- and n-layers. Semiconductor material absorbs a certain portion of the solar spectrum and adjacent layers (electrodes) are required to extract the photo-generated carriers for conveyance to an external electrical load.
The p-type layer in p-i-n devices is possible incident photons enter the intrinsic absorber layer (i-) of the device for conversion into charge carriers. This requires that all other “photo-passive” but functional layers in the PV cell that lie in the path of photons traversing to the absorber should not absorb or back reflect any of the light before it reaches the intrinsic absorber. That is, the window layers must be highly transparent, i.e., having a wider bandgap than the absorber and thus a much lower absorption coefficient in the spectral range of light used for photo-conversion. Electrically, the p-layer should have hole conduction in order to transport the photogenerated holes and block the electrons. Based on these requirements, the p-type layer in p-i-n devices should be the p-type transparent conducting oxides (p-TCOs).
The work performed in this thesis was therefore driven by two main objectives: (1) synthesis and understanding the fundamental physical properties (i.e., structural, electrical, and optical) of p-TCOs thin films; (2) design and investigating the multiferroic BFCO thin-film absorber based devices for efficient solar energy conversion applications including photodetectors, PV and PEC devices. The results obtained in this work are resumed in two sections as follows:
In the first section, we synthesized the p-type transparent conducting thin films and studied their structural, electrical and optical properties. (1) Perovskite p-type In-doped SrTiO₃ (SrInxTi1-xO₃ with In concentration in the range 0≤x≤0.15) thin films were grown on LaAlO₃ substrates using a pulsed laser deposition (PLD) and molecular beam epitaxy (MBE) combination technique. (2) The In-STO (ISTO, 0.1≤x≤0.15) films grown under oxygen pressure of 10⁻⁷ − 10⁻³ Torr show an optimal range of high transmittance (~70%), low resistivity (~10⁻² Ω cm), high carrier concentration of ~3×10¹⁹ cm⁻³ with mobility of ~5 cm²/Vs, and large Eg≥3.2 eV.
The second section is focused on solar energy conversion applications of BFCO thin films based devices: (1) the photodiodes based on the epitaxial BFCO/SrRuO₃ (SRO) thin films were fabricated by using PLD techniques. The photodiodes with a large ideality factor (n≈5.0) exhibits a substantial photocurrent at forward biased voltages (photoconductive effect) and a fast transient response (in the order of 10⁻² s). The tailoring of photoelectric performance was achieved by switching FE polarization state of BFCO (Eg≈2.5 eV; P≈40 μC cm⁻²). The ultrafast charge transfer at BFCO/SRO heterojunction was investigated by time-resolved photoluminescence. A peak sensitivity was measured as 0.38 mA/W at 500 nm by photoresponsivity spectroscopy. (2) We reported the fabrication of multiferroic BFCO thin films (Eg≈1.7−2.4 eV; P≈14−44 μC cm⁻²) based PV devices with p-i-n heterojunction by PLD. A p-type NiO thin film acting as hole-transporting/electron-blocking layer and a typical n-type Nb-STO acting as electron-transporting layer were used to form the double-interfaced heterojunctions. Under 1 sun illumination, the optimized p-i-n devices yielded an open-circuit voltage of ~0.53 V and a short-circuit current density of ~8.0 mA cm⁻², leading to a PCE of ~2.0%, a four-fold enhancement compared to that of the i-n device architecture. (3) The n-type BFCO thin films coated with a p-type transparent conducting NiO layer were implemented as a heterojunction photoelectrode by PLD for solar-driven water splitting. The tailoring of PEC performance of the bare BFCO (Eg≈1.8 eV; P≈20 μC cm⁻²) based photoanodes was achieved by effectively tuning the FE polarization state, and thus resulted in a 1.5-fold increase in photocurrent density. A 4-fold enhancement of photocurrent density, up to 0.4 mA cm⁻² (at +1.23 V vs. RHE) in 1 M Na₂SO₄ (pH 6.8) electrolyte under 1 sun illumination was carried out by coating the bare BFCO photoanodes with a p-type transparent conducting NiO layer acting as an electron-blocking and protection layer. The stable operation of p-NiO/n-BFCO heterojunction photoanodes was confirmed by observing a constant current density over 4 hours.


identifier: Imbrogno, Alessandra  (2018). Pulsed laser deposition based nanodecoration of carbon-based nanomaterials, their characterizations, and integration into third generation photovoltaic devices.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 87 p.

subject: électrodes

subject: ablation

subject: laser pulsée

subject: nano-décoration

subject: nanoparticules de Co/Ni

subject: nanomatériaux à

subject: base de carbone

subject: dye sensitized solar cells

subject: electrodes

subject: pulsed laser ablation

subject: nano-decoration

subject: Co/Ni nanoparticles

subject: carbon-based nanomaterials

subject: celle solari sensibilizzate con colorante

subject: elettrodi

subject: ablazione

subject: laser pulsata

subject: nano-decorazione

subject: nanoparticelle di Co/Ni

subject: nanomateriali a

subject: base di carbonio

abstract:
Le projet de thèse porte sur la synthèse et la caractérisation de nanomatériaux
à base de carbone et leur décoration subséquente par des nanoparticules en
utilisant la technique de déposition par ablation laser pulsée (ALP). L'objectif
ultime étant d'optimiser les conditions de décoration afin de développer de
nouvelles électrodes hautement performantes pour les cellules solaires
sensibilisées par colorant (communément connues sous le sigle DSCC pour "Dye
sensitized solar cells"). Les cellules solaires à colorant appartiennent à la
troisième génération de dispositifs photovoltaïques, et sont principalement
composées de deux électrodes (photoanode et cathode) déposées sur des
verres revêtus de fims de FTO (Fluorine-doped Tin Oxide) transparents et conducteurs électriquement. La photoanode, également appelée "électrode
de travail" ou "Working electrode (WE)", est constituée d'un film mince
de TiO₂, déposé sur un le verre revêtu de FTO, sensibilisé par un colorant
organique. La cathode, appelée "contre-électrode (CE)", est constituée d'un
film mince de platine pulvérisé sur un verre-FTO conducteur. L'espace entre
ces deux électrodes est rempli d'une solution d'électrolyte composée d'un
couple redox. Le grand avantage de ces dispositifs solaires par rapport aux
dispositifs solaires traditionnels, à base de silicium, réside dans les processus
de fabrication relativement simples et l'utilisation de matériaux abondants
sur la terre. Cependant, l'efficacité de conversion des DSSC est encore
modeste avec des efficacités de conversion atteignant à peine les 18% pour
les DSSC de type solide et les 10% pour les DSSC de type liquide. Les
principaux problèmes affectant l'efficacité photovoltaïque des DSSC sont la
détérioration du colorant, la forte recombinaison des paires électrons/trous
(e-/h+) dans le substrat de TiO₂, la résistance de contact entre la contre-
électrode et l'électrolyte, et la dégradation de la CE de platine dans la solution d'électrolyte. Au cours des deux dernières décennies, de nombreux efforts ont
été déployés pour résoudre ces problèmes, et certains progrès ont été faits en
modifiant à la fois les électrodes de travail et les contre-électrodes. Ce projet
de doctorat s'inscrit dans cette thématique de recherche visant à améliorer la
structure et les propriétés des matériaux formant les deux électrodes des cellules
DSSC de type liquide. Pour ce faire, nous avons opté pour l'utilisation
des nanomatériaux à base de carbone. Pour la contre-électrode, nous avons
démontré que le platine onéreux et instable dans l'électrolyte peut être
remplacé efficacement par des nanotubes de carbone multi-parois (MWCNT)
recouverts par des nanoparticules de Co-Ni déposées par ALP. Ces nouvelles
CE (moins coûteuses) assurent non seulement une bonne résistance à l'action
corrosive de la solution électrolytique, mais offrent également une plus grande
surface active qui améliore la catalyse de la réaction redox, résultant en
une amélioration significative de la performance photovoltaïque du dispositif
DSSC. Nous avons en effet pu corréler la performance de photoconversion
des DSSC à la rugosité de surface des CE formée par les nanoparticules de
Co-Ni. Du côté de l'électrode de travail, nous nous sommes concentré sur
l'insertion des différents nanomatériaux à base de carbone (les MWCNTs et
les feuillets de graphène) pour améliorer la conductivité des films de TiO₂
tout en réduisant les recombinaisons des paires (e-/h+). En combinant les
conditions de préparation optimales de nos CE et WE, nous avons réussi
à obtenir une efficacité de photoconversion maximale de 9.8% (qui est de
57% plus élevée que celles obtenues avec des CE de platine). Ces résultats
montrent clairement le potentiel de l'approche ALP pour la décoration des
électrodes par des nanoparticules métalliques ayant une haute pureté et
une grande adhésion à la surface. Ils ouvrent ainsi des perspectives fort
prometteuses pour des applications de DSSC.

The thesis project is focused on the synthesis and characterization of carbonbased
nanomaterials and their subsequent decoration by nanoparticles using
the pulsed laser ablation technique (PLA). The ultimate goal is to optimize
the conditions for the decoration in order to develop new high performance
electrodes for dye sensitized solar cells (commonly known as DSCC for "Dye
sensitized solar cells"). The dye solar cells belong to the third generation of
photovoltaic devices, and are mainly composed of two electrodes (photoanode
and cathode) deposited on glasses coated with electrically conductive and
transparent FTO films (Fluorine-doped Tin Oxide). The photoanode, also
called "Working electrode (WE)", consists of a thin fillm of TiO₂, deposited
on a glass coated with FTO, sensitized with an organic dye. The cathode,
referred to as the "counter electrode (CE)", consists of a platinum thin
film sprayed onto a conductive FTO-glass. The space between these two electrodes is filled with an electrolyte solution composed of a redox couple.
The great advantage of these solar devices over traditional silicon-based
solar devices is the relatively simple manufacturing processes and the use
of materials which are abundant on the Earth. However, the conversion
efficiency of DSSCs is still modest with conversion efficiencies as low as 18%
for solid DSSCs and 10% for liquid DSSCs. The main problems affecting the
photovoltaic efficiency of DSSCs are the deterioration of the dye, the strong
recombination of the electron / hole pairs (e- / h +) in the TiO₂ substrate,
the contact resistance between the counter-electrode and the electrolyte, and
degradation of platinum CE in the electrolyte solution. Over the last two
decades, many efforts have been made to address these problems, and some
progress has been made in modifying both the working and the counter
electrodes. This doctoral project is part of this research theme aimed at
improving the structure and properties of the materials forming the two
electrodes of liquid-type DSSC cells. To do this, we opted for the use of
carbon nanomaterials. For the counter-electrode, we have demonstrated
that platinum that is expensive and unstable in the electrolyte can be effectively
replaced by multiwall carbon nanotubes (MWCNT) coated with
PLA-deposited Co-Ni nanoparticles. These new (cheaper) CEs not only
provide good resistance to the corrosive action of the electrolytic solution,
but also provide a larger active surface that improves the catalysis of the redox reaction, resulting in a signi_cant improvement in the photovoltaic
performance of the DSSC device. We have indeed correlated the photoconversion
performance of DSSC with the surface roughness of the CE formed by
the nanoparticles of Co-Ni. On the working electrode side, we focused on the
insertion of the various carbon-based nanomaterials (MWCNTs and graphene
sheets) to improve the conductivity of TiO₂ films while reducing recombination
of pairs (e - / h +). By combining the optimal preparation conditions
of our CE and WE, we achieved a maximum photoconversion efficiency of
9.8% (which is 57% higher than those obtained with platinum CEs). These
results clearly show the potential of the ALP approach for the decoration of
electrodes by metal nanoparticles having a high purity and a great adhesion
to the surface. They open up very promising prospects for DSSC applications.

Il progetto di tesi è incentrato sulla sintesi e caratterizzazione di nanomateriali a base di carbonio e sulla loro successiva decorazione mediante nanoparticelle utilizzando la tecnica di ablazione laser pulsata (PLA). L'obiettivo finale è
quello di ottimizzare le condizioni per la decorazione al fine di sviluppare
nuovi elettrodi ad alte prestazioni per celle solari sensibilizzate con coloranti
(comunemente note come DSCC, "Dye-sensitized Solar Cells"). Le celle
solari con colorante appartengono alla terza generazione di dispositivi fotovoltaici
e sono principalmente composte da due elettrodi (fotoanode e catodo)
depositati su vetri rivestiti con film FTO elettricamente conduttivi e trasparenti
(ossido di stagno drogato con uoro). Il fotoanodo, chiamato anche
"working electrode (WE)", consiste in un film sottile di TiO₂, depositato
su un vetro rivestito di FTO, sensibilizzato con un colorante organico. Il
catodo, indicato come "controelettrodo (CE)", è costituito da un film sottile
di platino spruzzato su un vetro FTO conduttivo. Lo spazio tra questi due
elettrodi è riempito con una soluzione elettrolitica composta da una coppia
redox. Il grande vantaggio di queste celle solari rispetto ai tradizionali dispositivi
basati sul silicio sono i processi di produzione relativamente semplici e l'uso di materiali che sono abbondanti sulla Terra. Tuttavia, l'efficienza
di conversione delle DSSC è ancora modesta con efficienze di conversione
inferiori al 18% per le DSSC a stato solido e al 10% per le DSSC a stato
liquido. I principali problemi che riguardano l'efficienza fotovoltaica delle
DSSC sono il deterioramento del colorante, la forte ricombinazione delle
coppie di elettroni / lacune (e- / h +) nel substrato di TiO₂, la resistenza
di contatto tra il contro-elettrodo e l'elettrolita, e degradazione del CE di
platino nella soluzione elettrolitica. Negli ultimi due decenni, sono stati fatti
molti sforzi per risolvere questi problemi e sono stati fatti alcuni progressi
nella modifica sia dei fotoanodi che dei contro-elettrodi. Questo progetto di
dottorato fa parte del filone di ricerca volto a migliorare la struttura e le
propriet_a dei materiali che formano i due elettrodi delle cellule DSSC di tipo
liquido. Per fare questo, abbiamo optato per l'uso di nanomateriali di carbonio.
Per il contro-elettrodo, abbiamo dimostrato che il platino che è costoso
e instabile nell'elettrolita può essere efficacemente sostituito da nanotubi di
carbonio a pareti multiple (MWCNT) rivestiti con nanoparticelle di Co-Ni
depositate con PLA. Questi nuovi CE (meno costosi) non solo forniscono una buona resistenza all'azione corrosiva della soluzione elettrolitica, ma
forniscono anche una superficie attiva più ampia che migliora la catalisi della
reazione redox, determinando un significativo miglioramento delle prestazioni
fotovoltaiche del dispositivo DSSC. Abbiamo infatti correlato le prestazioni
di fotoconversione della DSSC con la rugosità superficiale del CE formato
dalle nanoparticelle di Co-Ni. Sul lato del fotoanodo, ci siamo concentrati
sull'inserimento di vari nanomateriali a base di carbonio (MWCNT e fogli di
grafene) per migliorare la conduttività dei film di TiO₂ riducendo la ricombinazione
delle coppie (e - / h +). Combinando le condizioni di preparazione
ottimali dei nostri CE e WE, abbiamo ottenuto un' efficienza di fotoconversione
massima del 9,8% (che è del 57% superiore a quella ottenuta con CE di
platino). Questi risultati mostrano chiaramente il potenziale dell'approccio
PLA per la decorazione di elettrodi da parte di nanoparticelle metalliche con
un'elevata purezza e una grande adesione alla superficie, aprendo prospettive
molto promettenti per le applicazioni nelle DSSC.


identifier: Jeon, Jinwoo  (2018). A programmable passive amplifier based on temporal self-imaging (Talbot) effect and application.  Mémoire.  Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en télécommunications, 108 p.

subject: télécommunications

abstract:
The temporal Talbot effect, also referred to as temporal self-imaging effects (TSI) is observed when a periodic pulse train propagates through a first-order dispersive medium. Under specific dispersion conditions, either an exact or a repetition-rate multiplied self-image of the input signal is reproduced at the output. Moreover, the TSI possesses an interesting self-restoration capability, which proves effective even when acting over an aperiodic train of pulses. Besides its compelling interest as a physical phenomenon, the TSI has additionally been put into practice in several areas.
This work targets application of TSI in two different fronts, namely for signal intensity amplification and for clock recovery in telecommunication systems, with a focus on optical-domain waveform processing. On the one hand, signal intensity amplification is an essential process in plentiful of applications, including for initiating physical processes, diagnostics, sensing, communications and measurement, just to name a few. On the other hand, clock recovery (CR) from data coded signals is a fundamental functionality to establish the needed synchronization in high-speed telecommunication links and signal-processing platforms, including systems based on optical signals. In these two applications, the notion of programmability is of fundamental importance. To begin with, it is obvious that for any amplification system, the capability of tuning the amplifier gain is crucial for a practical, real-world use of the amplifier. In regards to the CR problem, it should be noted that it is often desired to have access to the capability of recovering a clock signal (e.g., periodic pulse train), synchronized with the incoming data packet, with a pulse rate either identical to the symbol rate of the data signal (base-rate CR, or BR-CR) or at a divided rate with respect to the input data (sub-harmonic CR, or SH-CR). SH-CR is particularly interesting in the context of time-division multiplexing systems. The capability of tuning the clock rate with respect to the input data provides an additional important versatility in the telecommunication or signal-processing platform at hand.
An advanced new feature of TSI, referred to as inverse temporal self-imaging (I-TSI), has been recently reported that enables to obtain a self-image of an incoming periodic temporal waveform (e.g., optical pulse train) but with a divided repetition rate. This is achieved through a lossless process that incorporates a suitably designed temporal phase-modulation stage before the dispersive medium. I-TSI has been demonstrated for passive amplification of repetitive optical waveforms, as induced by a lossless repetition-rate division of the incoming waveform, as well as to recover the sub-harmonic clock signal from pulsed telecommunication data signals. Unfortunately, in previous designs for passive waveform amplification and sub-harmonic clock recovery based on I-TSI, a different gain factor or a different clock rate-division factor required the use of a different amount of dispersion, a significant and unpractical modification in the amplifier setup. The possibility of achieving a reconfigurable gain factor or rate division factor in these systems constitutes the central scope of this work. In this context, the main contribution reported in this thesis resides in the derivation of a non-trivial generalization of the I-TSI equations (i.e., designing equations for the phase modulation and dispersive stages), which allow us to obtain a relatively wide range of different gain factors, or the associated rate-division factors, using a fixed dispersion, by suitably programming the temporal phase modulation step. Such a reconfigurability can be achieved by electronic means using an electro-optic phase modulator for implementation of the temporal phase modulation step. Experimental results are reported to validate the newly proposed design for passive Talbot amplification of repetitive optical waveforms in which the gain factor can be electrically reconfigurable. An all-fiber design is also demonstrated for a programmable base/sub-harmonic optical clock recovery circuit from pulsed (return-to-zero, RZ) telecommunication data signals, in which the divided clock rate can be electrically reconfigurable as well.


identifier: Li, Jinxin  (2018). Reconfigurable antennas using frequency selective surfaces.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en télécommunications, 132 p.

subject:
telecommunications
reconfigurable antennas

abstract:
Nowadays, because of the requirements of miniaturization and multifunction in the modern
communication systems, more and more electronic devices are integrated into a single platform.
By using this method, the communication quality can be improved significantly. However,
another serious problem of interference has been introduced. As a solution for resolving this
issue to enhance the performance of communication systems, radiation pattern reconfigurable
antennas have received much attention. The conventional methods for designing radiation pattern
reconfigurable antennas based on the phased antenna arrays incur large loss, and are complicated
and expensive to be applied in practice. For this issues, frequency selective surfaces (FSSs) work
as space filters to electromagnetic (EM) waves, which can be either transmitted or reflected in
the operating frequency band. Therefore, radiation pattern reconfigurable antennas are realized
by using frequency selective surface (FSS) in this thesis. This approach offers more antenna
functionality, less cost and a significant save in terms of size and space. Thus, research in this
field is very important and is one of the most popular fields nowadays.
In this dissertation, first and foremost, a novel dual-band beam-sweeping antenna based on two
independent cylindrical active frequency selective surfaces (AFSS) have been proposed. As the
AFSS unit cell characteristic is the primary influential parameter that affects the sweeping
radiation pattern functionality. Hence, two AFSS unit-cells with integrated pin-diodes have been
proposed at two different frequency bands, 2.45 GHz and 5.2 GHz. When a dual-band
omnidirectional monopole antenna is surrounded by two cylindrical AFSS screens, the proposed
design has shown that it can effectively realize beam-sweeping which covers all azimuth angles
at 2.45 GHz and 5.2 GHz simultaneously. The size of antenna system can be reduced greatly in
comparison with the case where the two cylindrical FSS screens work independently from each
other when they are loaded in the same antenna system.
Secondly, a beam-switching antenna with high gain and flexible control of beam numbers has
been proposed based on FSS. The proposed antenna is composed of an omnidirectional
monopole antenna as a radiating source surrounded by a hexagon FSS screen and six metallic
sheets. By changing the states of the pin-diodes in the hexagon FSS screen, the proposed antenna
can not only sweep the beam six directions with gain enhancement in the azimuth plane, but also
it can flexibly operates at multiple beam modes at 5.2 GHz. Then, a beam-tilting antenna with negative refractive index metamaterial (NRIM) loading has
also been designed. The proposed antenna is composed of a double-feed dielectric resonator
antenna (DRA) and 1×4 NRIM array, which is fixed over and in the middle of the DRA. This
beam-tilting antenna can steer the main beam by ±38o in the xoz-plane over 5 to 5.5 GHz band.
The reflection coefficient of the antenna is better than -10 dB in the band from 5 to 5.5 GHz.
In the final design, a three layers quasi-yagi antenna has been designed with multi- beam
directions in both elevation and azimuth plane at 5.2 GHz. There are four elements of quasi-Yagi
antenna and eight pin-diodes as switches inserted them in the middle layer. The top and bottom
layers include the parasitic elements each of which are inserted into pin-diodes. By controlling
the pin-diodes in the different layers, the antenna can realize beam switching in the azimuth
plane in four directions and beam tilting in the elevation plane.


identifier: Memmi, Amen  (2018). Systèmes bayésiens de notation: analyse et améliorations.  Mémoire.  Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en télécommunications, 121 p.

subject:
système de notation
competence
inférence Bayésienne
propagation de messages
statistiques du jeu
rating system
skills
bayesian inference
message passing
in-game statistics

abstract:
Les systèmes de notation continuent de faire l’objet d’un intérêt croissant, en particulier après la
popularité croissante des jeux multijoueur en ligne. La plupart de ces derniers basent le jumelage des
joueurs sur leurs compétences afin de leur donner des matchs équitables et agréables. L’estimation
de ces compétences est réalisée à travers un système de notation qui les déduit à partir des
données historiques. Le système de notation bayésien TrueSkill™, développé il y a quelques années
par Microsoft, fournit un modèle probabiliste pour cette estimation dans un cadre général de
compositions et de nombre d’équipes et ce seulement à partir du résultat binaire de chaque match.
Dans ce travail, on présente et on analyse le comportement de ce système dans des situations
particulières et on se propose ensuite de l’étendre en incorporant les différentes statistiques disponibles
relatives au déroulement des jeux, telles que le nombre de kills, les dégâts moyens reçus, le nombre
de matchs déjà joués et plein d’autres caractéristiques. On montre que l’extension et les modifications
apportées permettent des gains importants capturés par les multiples métriques d’évaluation introduites.
Entre autres, la corrélation des mises à jour des compétences par ces statistiques a permis au système
des prédictions plus précise, ayant un plus grand gain d’information, plus équitable en relation avec
les performances individuelles et mieux représentative des compétences moyennes de certaines sous
populations de joueurs définies à travers les statistiques.

 Rating systems continue to attract increasing interest, especially after the growing popularity
of online multiplayer games. Most of the latter base the matching of players on their skills in order
to give them fair and enjoyable matches. These skills are estimated using a rating system that
derives them from historical data. The TrueSkill™Bayesian rating system, developed a few years
ago by Microsoft, provides a probabilistic model for this estimation within a general framework
of teams composition and number and inference is done based only on the binary result of each
match. In this work, we present and analyze the behavior of this system in particular situations
and we then propose to extend it by incorporating the various available in-game statistics, such as
the number of kills, the average damage received, the number of matches already played and many
other characteristics. We show that the extension and the modifications made allow significant gains
captured by the multiple metrics of evaluation introduced. Among other things, the correlation of
skills updates by these statistics has allowed the system to make predictions that are more accurate,
having a greater gain of information, more equitable in relation to individual performances and with
better representative capacity of the average skills of certain statistics-defined sub-populations.


identifier: Nono Kamga, Gervais  (2018). Modeling and analysis of wireless information and energy transmission in MIMO systems.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en télécommunications, 91 p.

subject:
wireless power transfer
multiple-input multiple-output antenna
MIMO
WPT

abstract:
The next generation of wireless communications systems are expected as a revolution
in the area of telecommunications, where they promise tremendous network capacity,
huge data rates for very high number of end users and simultaneous supported connections
with large sensor deployments, as well as very high gains in terms of spectral
efficiency, energy efficiency, latency, and coverage. To allow the emergence of such
networks, it is necessary to satisfy the fundamental needs of available energy supply,
and spectrum availability/efficient usage.
The wireless power transfer (WPT) techniques are shown to be strong, reliable
with the potential to replace the currently-used yet painstaking wired charging; providing
the end users with almost unlimited energy sources. Due the outstanding advantages
these techniques promise, both academic world and the industry are actively
investigating solutions for allowing networks to implement WPT, where the operating
nodes can simultaneously harvest/transmit energy, while processing data signals.
On the other hand, for solving the spectrum efficient usage/availability issue, improving
the spectral efficiency has been extensively investigated through the several past
years, and represents a very strong solution. In this regards, regular multiple-input
multiple-output (MIMO) antenna technique, since the last decade, and, more recently,
massive MIMO; have been widely exploited and are powerful wireless technologies for
tremendously improving the spectral efficiency, and even energy efficiency.
Thanks to the above capabilities of regular- and massive MIMO, and of the WPT,
these techniques have become strong candidates for the development and the emergence
of the next-generation wireless communications networks. Considering that
the theoretical understanding and practical deployment of these systems requires to
first evaluate their performances, while taking into account various key propagation
and networks characteristics; this thesis aims to provide a framework for channel modeling and performance analysis of next-generation wireless communications networks,
with information processing and energy harvesting, and implementing regularand/
or massive MIMO. More specifically, as a first step, in the initial part of the
thesis, a generalized analysis for the spectral efficiency of both regular- and large-scale
(massive) MIMO systems is performed, where major radio-propagation characteristics
and antenna-array parameters are taken into account, including path loss, shadowing
effect, multi-path fading, antenna correlation, antenna polarization, environmental
cross-polarization coupling and antenna cross-polarization discrimination.
The second step of the thesis conducts the modeling and performance analysis of
massive MIMO systems in terms of spectral efficiency, in both the centralized and
the distributed configurations, referred to as centralized (C-MIMO) and distributed
(D-MIMO), respectively. This is based on a novel comprehensive channel model,
which accounts for real environmental parameters and antenna characteristics, namely,
path loss, shadowing effect, multi-path fading and antenna correlation.
In the third part of the thesis, WPT is investigated. This is done by considering
massive MIMO WPT systems, operating in millimeter wave (mmWave) bands; where
both the rainy and non-rainy conditions are considered, and the channel model accounts
for rainfall effects, path loss and fast fading. Then, finally, the fourth step
of the thesis investigates the performance of networks with simultaneous energy harvesting
and information transmission. The considered system implements massive
MIMO, and operates in the mmWave bands, while accounting for rainfall effect, path
loss and fading.
While conducting the work, the adopted methodology consists of modeling the
channel, by considering major radio-propagation characteristics and antenna-array
parameters; then conducting the performance analysis, in terms of the spectral efficiency
(in the first two parts of the thesis), the harvested energy (in the third part),
and the throughput (in the fourth part). These metrics are all derived in closed-form
then studied in various key practical scenarios, to obtain important insights which
are not only highly important for the comprehension of the different technologies
in future networks, but will also benefit system designers and manufacturers in the
design of these systems and their operating nodes.