La connaissance de la dynamique des matières en suspension (MES) et des turbidités en milieu côtier est un élément clé pour comprendre les écosystèmes marins. Les processus de floculation/défloculation représentent des mécanismes essentiels contrôlant la dynamique des caractéristiques physiques des MES et, par conséquent, leur devenir dans l’environnement. Cette thèse a pour objectif de mieux comprendre la caractérisation des MES et leur variabilité de l’échelle tidale à l’échelle annuelle en mer côtière, en réponse aux différents forçages hydrodynamiques, hydrologiques et biologiques ayant lieu à l’interface entre estuaire et baie. À cette fin, des capteurs optiques et acoustiques ont été déployés in situ, lors de 6 campagnes en mer réalisées en 2016, en vue de caractériser et de quantifier les MES dans la colonne d’eau, à la sortie de l’embouchure de l’estuaire de Seine (France). Une analyse critique des mesures granulométriques issues du LISST-100X est proposée. Un travail de quantification des incertitudes de mesure associées à l’estimation de la concentration en MES a mis en avant le risqué lié à un rinçage insuffisant des filtres et a conduit à définir une masse minimum à filtrer, de l'ordre de 10 mg, quelle que soit la concentration. Ce travail a notamment permis de proposer une méthode d’estimation d’un volume optimal de filtration basée sur une mesure préalable de turbidité de référence. Les mesures à haute fréquence ont montré que la dynamique des caractéristiques physiques des MES en termes de concentration et de taille médiane sont contrôlées par le cycle advection-floculation-sédimentation-remise en suspension. Ces résultats ont permis de hiérarchiser les paramètres de contrôle des processus de floculation. La turbulence a été identifiée comme le principal paramètre de contrôle à l’échelle tidale et semi-lunaire, la taille médiane maximale des flocs étant inversement corrélée à l’intensité des courants. À l’échelle saisonnière, la variation des caractéristiques des MES (taille, densité, vitesse de chute) est liée à la variabilité du contenu en matière organique (MO), avec une floculation favorisée quand le taux de MO particulaire augmente. Ces flocs plus grands et moins denses sont également plus résistants à la fragmentation induite par cisaillement turbulent. Ces travaux ont également permis de discuter le concept de structuration fractale des flocs.La dynamique de la dimension fractale, déterminée en combinant des données in situ de concentration en MES et de distribution en classe de taille, peut traduire des variations de composition des MES, mais peut aussi résulter d'incertitudes de mesure associées aux instruments. Ces dernières sont discutées dans cette thèse. La variabilité saisonnière des caractéristiques des MES est plus prononcée au large que dans la zone sous influence de l’estuaire de Seine. À partir des observations ponctuelles en Baie de Seine et d’une série de mesure long terme dans la zone côtière belge acquise par le laboratoire RBINS, les méthodes acoustiques et optiques sont combinées. Ces dernières ont mis en avant une augmentation de la rétrodiffusion acoustique lorsque la densité moyenne des flocs diminue. / The knowledge of suspended particulate matter (SPM) and turbidity dynamics in coastal waters is essential for studying marine ecosystems. Flocculation/deflocculation processes are crucial mechanisms controlling the dynamics of SPM physical characteristics and thus, the fate of these SPM in the environment. This PhD thesis focuses on the SPM characteristics and their dynamics in coastal waters, from tidal to annual scales, in response to hydrodynamic, hydrological and biological forcing that take place at the interface between estuaries and coastal seas. To this end, optical and acoustic sensors were deployed in situ through 6 field campaigns in 2016, in order to characterize and quantify SPM in the water column, near the mouth of the Seine estuary (France). A critical analysis of LISST-100X measurements in coastal waters is presented. The quantification of uncertainties on SPM concentration measurements is investigated: it highlights the crucial effect of salt retention, and the need for a minimum mass to filter, around 10 mg. A method for estimating an optimal filtration volume based on a reference turbidity measurement is proposed. High frequency measurements show that the dynamics of SPM and median diameter are controlled by the advection-flocculationsedimentation-resuspension cycle.These results allow to classify the factors controlling flocculation processes. Turbulence is identified as the main factor at the semi-diurnal and semi-lunar tidal scales, as the maximum median size of flocs decreases when the tidal currents intensify.At the seasonal scale, the variation of SPM characteristics (size, density, settling velocity) is correlated to the variability of the organic matter (OM) content: in particular, flocculation is enhanced by an increase of the particular OM fraction. The resulting larger and lesser dense flocs are also more resistant to the fragmentation induced by shear. This work also investigates the fractal approach applied to flocs. The fractal dimension variability, calculated by combining in situ data of SPM concentration and particle size distribution, can be associated to variations of the SPM composition, but can also result from uncertainties linked to instrument limitations. The latter are discussed in this PhD thesis. The seasonal variability of SPM characteristics is more pronounced offshore than at the mouth of the Seine estuary. From short-term observations in the Seine Bay and from long-term series in the Belgian coastal zone provided by the RBINS, optical turbidity and acoustic backscatter measurements are combined. They highlight an increase of the acoustic backscatter intensity when mean floc density.

Disertační práce se zabývá bezkontaktní analýzou vibrací pomocí metod akustické holografie v blízkém poli. Akustická holografie v blízkém poli je experimentální metoda, která rekonstruuje akustické pole v těsné blízkosti povrchu vibrujícího předmětu na základě měření akustického tlaku nebo akustické rychlosti v určité vzdálenosti od zkoumaného předmětu. Konkrétní realizace této metody závisí na použitém výpočetním algoritmu. Vlastní práce je zaměřena zejména na rozbor algoritmů, které využívají k rekonstrukci zvukového pole v blízkosti vibrujícího objektu transformaci do domény vlnových čísel (prostorová transformace), kde probíhá vlastní výpočet. V úvodu práce je vysvětlena základní teorie metody akustické holografie v blízkém poli s popisem základních vlastností a dále rozborem konkrétních nejčastěji používaných algoritmům pro lokalizaci a charakterizaci zdroje zvuku a pro následnou vibrační analýzu. Stěžejní část práce se věnuje pokročilým metodám zpracování, které se snaží určitým způsobem optimalizovat přesnost predice zvukového pole v blízkosti vibrujícího předmětu v reálných podmínkách. Jde zejména o problematiku použitého měřicího systému s akustickými snímači, které nejsou ideální, a dále o možnost měření v prostorách s difúzním charakterem zvukového pole. Pro tento případ byla na základě literárního průzkumu optimalizována a ověřena metoda využívající dvouvrstvé mikrofonní pole, které umožňuje oddělení zvukových polí přicházejících z různých stran a tedy úspěšné měření v uzavřených prostorách např. kabin automobilů a letadel. Součástí práce byla také optimalizace, rozšíření a následné ověření algoritmů publikovaných v posledních letech pro měření v reálných podmínkách za použití běžně dostupných akustických snímačů.

La dynamique des Matières en Suspension (MES) dans les estuaires macrotidaux est fortement variable à la fois spatialement (du compartiment fluvial à l'embouchure de l'estuaire) et temporellement (de la seconde à plusieurs années), mais reste primordiale pour comprendre et quantifier la dynamique sédimentaire des environnements estuariens. Avec le développement croissant des réseaux de mesures haute-fréquence à l'échelle internationale, l'objectif principal de cette étude est de qualifier et de valoriser les mesures de turbidité acquises par un réseau de mesures haute fréquence (réseau SYNAPSES) implanté d'amont en aval sur l'estuaire de la Seine (France) à la fois (i) en matière de suivi de la dynamique des MES du compartiment fluvial au bouchon vaseux et (ii) en matière d'estimation des flux de MES sur différentes échelles spatio-temporelles de l'estuaire de la Seine. Les données acquises à partir du réseau SYNAPSES et des campagnes in situ (81 journées de 12 h - OBS-3+/YSI/LISST 100X-C/ADCP 600 kHz) sur quatre stations réparties de l'estuaire fluvial à la zone du bouchon vaseux, constituent un set de données extrêmement riche et unique sur les domaines estuariens. La variabilité des relations, établies entre les mesures de turbidité [NTU] et les mesures de concentrations en MES [g.L-1] sur chacune des campagnes de l'échelle tidale à annuelle, met en évidence l'effet (i) de la technologie interne du capteur et (ii) de la variabilité des propriétés optiques inhérentes des particules (diamètre médian D50), densité sèche rhô et efficacité de diffusion Qc) sur la sensibilité des différents capteurs optiques. L'analyse conjointe des données in situ et des données SYNAPSES a permis de calibrer les mesures de turbidité en concentration massique, avec une relation validée sur le cycle annuel, spécifique à chacune des stations et des incertitudes minimisées. Après une étude de la représentativité des stations du réseau vis-à-vis de la section, les flux instantanés de MES sont estimés (i) à partir des données de concentrations en MES et de débits acquis par l'ADCP sur l'intégralité de la section et (ii) à partir des concentrations ponctuelles en MES du réseau SYNAPSES couplées au modèle hydrodynamique MARS-3D. Les comparaisons des flux de MES in situ par rapport à ceux estimés par la combinaison SYNAPSES/MARS-3D permettent de proposer un coefficient spécifique à chacune des stations du réseau SYNAPSES, dans le but d'ajuster les flux instantanés de MES estimés, avec leurs incertitudes, à partir du réseau SYNAPSES à la réalité in situ. Les outils et les démarches développés dans la thèse sur l'estuaire de la Seine pauvent être appliqués à d'autres estuaires macrotidaux pour estimer les flux sédimentaires. / The dynamics of Suspended Particulate Matter (SPM) in macrotidal estuaries is highly variable both spatially (from the fluvial compartment to the estuary mouth) and temporally (from the second to several years), but it is essential to understand and quantify the sedimentary dynamics of estuarine environments. With the development of high-frequency measurement networks around the world, the main objective of this study is to qualify the turbidity measurements acquired by a high-frequency measurement network (SYNAPSES network) located on the Seine estuary (i) in terms of monitoring the SPM dynamics from the fluvial compartment to the turbidity maximal zone (TMZ) and (ii) in terms of estimation of the SPM fluxes on different spatio-temporal scales of the Seine estuary. Data acquired from the SYNAPSES network and complementary in situ campaigns (81 days of 12 h - OBS-3+/YSI/LISST 100X-C / ADCP 600 kHz) on four stations from the fluvial estuary of the Seine Estuary to the turbidity maximal zone, are an extremely rich and unique dataset on estuarine environments. The variability in the relationship between turbidity measurements [NTU] and SPM concentration measurements [g.L-1] on each campaign, reveals the effect of (i) the internal sensor technology and (ii) the variability of the particle inherent optical properties (median diameter D50, dry density rho and scattering efficiency Qc) on the sensitivity of different optical sensors. The analysis of the in situ and the SYNAPSES data allowed to calibrate the turbidity measurements in mass concentration, with a validated relationship on the annual cycle, specific to each of the stations and reduced uncertainties. After a study of the SYNAPSES station representativeness across the section, the instantaneous fluxes of SPM are estimated (i) from the SPM concentration and liquid flow data acquired by the ADCP on the global section and (ii) from the SPM concentrations of the SYNAPSES network coupled to the hydrodynamic model MARS-3D (estimation of the liquid flow). Comparisons of SPM fluxes in situ to those estimated by the combination SYNAPSES/MARS-3D allow to propose a specific coefficient for each of the SYNAPSES network stations, xith the aim of adjusting the SPM instantaneous fluxes estimated from the SYNAPSES network to the in situ reality, with reasonable uncertainties. the tools and approaches developed in the PhD thesis on the Seine estuary can be applied to other macrotidal estuaries to estimate sedimentary fluxes.

<div> The Unmanned Aerial Vehicles (UAV) technology has evolved exponentially in recent years. Smaller and less expensive devices allow a world of new applications in different areas, but as this progress can be beneficial, the use of UAVs with malicious intentions also poses a threat. UAVs can carry weapons or explosives and access restricted zones passing undetected, representing a real threat for civilians and institutions. Acoustic detection in combination with machine learning models emerges as a viable solution since, despite its limitations related with environmental noise, it has provided promising results on classifying UAV sounds, it is adaptable to multiple environments, and especially, it can be a cost-effective solution, something much needed in the counter UAV market with high projections for the coming years. The problem addressed by this project is the need for a real-world adaptable solution which can show that an array of acoustic sensors can be implemented for the detection and localization of UAVs with minimal cost and competitive performance.<br><br></div><div> In this research, a low-cost acoustic detection system that can detect, in real time, about the presence and direction of arrival of a UAV approaching a target was engineered and validated. The model developed includes an array of acoustic sensors remotely connected to a central server, which uses the sound signals to estimate the direction of arrival of the UAV. This model works with a single microphone per node which calculates the position based on the acoustic intensity change produced by the UAV, reducing the implementation costs and being able to work asynchronously. The development of the project included collecting data from UAVs flying both indoors and outdoors, and a performance analysis under realistic conditions. <br><br></div><div> The results demonstrated that the solution provides real time UAV detection and localization information to protect a target from an attacking UAV, and that it can be applied in real world scenarios. </div><div><br></div>

According to the 2019 Canadian infrastructure report card, a concerning amount of municipal infrastructure is in poor or very poor condition. The infrastructure in this condition requires immediate action for rehabilitation or replacement. For concrete infrastructure, an effective repair can extend its service life and ensure that the services it provides continue to meet the community expectations. However, unfavorable environmental factors such as repeated/cyclic loads and freezing and thawing cycles adversely affect the bond between substrate concrete and repair materials, which lowers the structural capacity of repaired structures. So far, researchers have found that bond strength of repair can be affected by surface roughness, surface moisture, chemical adhesion or cohesion, curing regime, properties of substrate and repair materials, use of bond agent, and curing regimes. These findings are mostly based on the studies that focused on cold-jointed cylinders or beams, but in real-life repair situations, repairs of beams or slabs are located at either tension or compression side of the structure. Currently, there is no comprehensive study that investigates the bond of concrete repair under a combination of freezing and thawing and repeated/cyclic loading conditions. In addition, it is challenging to provide a rapid and non-destructive evaluation of the bond deterioration of repair materials. To address these issues systematically, this dissertation breaks the task into four phases. Phase (I) focuses on the development of an engineered “crack-free” repair mix that contains polypropylene (PP) fiber. A novel method is used to surface treat the PP fibers with supplementary cementitious materials. The effectiveness of surface-treating fibers for improved bond strength and reduced cracking is investigated. The compressive, tensile, and flexural strength of this engineered repair mix are determined and compared with two commercially available repair materials. The results from Phase I show that by adding 0.2% (by weight) Metakaolin-treated fibers into concrete mix, the compressive strength improves by up to 15.7% compared to mixes with untreated fibers. This study achieved a strength increase of 13.5% as compared to the reported 3.3% in other studies that use 25 times the amount of metakaolin used in this study. The experimental results confirm that at 0.2% dosage level, the use of novel surface treating technique is a cost-effective way to improve the strength of repair materials. Phase (II) focuses on characterizing the bond strength of various repair systems after freezing-thawing (FT) damage using both non-destructive and destructive methods. Two innovative sounding methods, which overcome the subjectivity of the traditional chain drag method, are used to evaluate FT damage non-destructively. In the experimental study, beams with a U-shaped cut are made to simulate conditions experienced by a concrete structure during a typical repair project. Three types of repair materials are used including cementitious repair concrete, cementitious repair mortar, and polymer-modified cementitious mortar. After up to 300 cycles of freeze-thaw exposure, resonant frequency and bond flexural strength of the prismatic specimens are determined. The empirical equations relating Non-destructive test (NDT) measurements and flexural bond strength of the repaired structures after freeze-thaw (FT) exposure are proposed. The results from Phase II show that the change in dynamic modulus of elasticity determined from NDTs agrees well with the change in other measurements including flexural bond strength, interfacial crack width, and mass loss after freeze-thaw exposure. In this study, linear relationships are established between dynamic modulus of elasticity and flexural bond strength for both cementitious and polymer-modified cementitious repair mortar with a coefficient of determination ranging between 0.87 and 0.95. The proposed empirical models can be used to predict bond flexural strength of repaired structures based on NDT measurement. Also, it was found that the samples repaired with polymer-modified cementitious mortar (Mix P) have superior FT resistance compared to other repaired samples. Phase (III) focuses on investigating the structural capacity and bond performance of repaired beams after cyclic/repeated loading. To accelerate the test process, a novel modified loading regime consisting of cycle groups of increasing cyclic/repeated stress amplitude is proposed. The models proposed by literature and current codes and standards are used to validate the results. Phase (IV) focuses on the development of the damage models for both individual and combined FT and cyclic loading exposure on repaired concrete structures. The results in phase III show the feasibility of using the Palmgren-Miner rule and Goodman linear model to estimate the fatigue life of repaired structures. This was confirmed within the context of this study. This study established the usefulness of using groups of increasing cyclic stress amplitude to accelerate the fatigue test process. The two-million cycle fatigue endurance limit estimated using cycle groups of Mix S (70.8%) was very similar to what was reported in the literature (71%) using the traditional time-consuming cyclic loading method. This study found that the formulas proposed by CSA 23.3 can effectively predict the moment resistance of both intact (control) and repaired RC beams. The ratio of experimental moment resistance values to its predictions ranges from 0.91 to 1.04. Based on the experimental results of previous three phases, an empirical model that predicted the fatigue service life of FT-damaged concrete structures is proposed. Future research requires a more comprehensive study on the FT performance of various polymer-modified cementitious mortars of different mix designs in repairing concrete structures. By increasing the number of tested specimens, a better relationship could be established between destructive and NDT methods. Future research is also required to explore the combined effect of FT and cyclic loading on repaired RC structures experimentally. / Graduate / 2023-03-22

No description available.