This thesis provides theoretical and practical solutions to two problems raised by digital photography of moving scenes, and infrared photography. Until recently photographing moving objects could only be done using short exposure times. Yet, two recent groundbreaking works have proposed two new designs of camera allowing arbitrary exposure times. The flutter shutter of Agrawal et al. creates an invertible motion blur by using a clever shutter technique to interrupt the photon flux during the exposure time according to a well chosen binary sequence. The motion-invariant photography of Levin et al. gets the same result by accelerating the camera at a constant rate. Both methods follow computational photography as a new paradigm. The conception of cameras is rethought to include sophisticated digital processing. This thesis proposes a method for evaluating the image quality of these new cameras. The leitmotiv of the analysis is the SNR (signal to noise ratio) of the image after deconvolution. It gives the efficiency of these new camera design in terms of image quality. The theory provides explicit formulas for the SNR. It raises two paradoxes of these cameras, and resolves them. It provides the underlying motion model of each flutter shutter, including patented ones. A shorter second part addresses the the main quality problem in infrared video imaging, the non-uniformity. This perturbation is a time-dependent noise caused by the infrared sensor, structured in columns. The conclusion of this work is that it is not only possible but also efficient and robust to perform the correction on a single image. This permits to ensure the absence of ''ghost artifacts'', a classic of the literature on the subject, coming from inadequate processing relative to the acquisition model.

The work in this dissertation comprises aeroservoelastic simulation development, two modal filter design case studies and theoretical improvement of the modal filter. The modal filter is made robust to sensor bias. Studies have shown that the states estimated by the modal filter can be integrated into active structural control. The integration of modal filters into aircraft structural control systems is explored. Modal filters require distributed sensing to achieve accurate modal coordinate estimates. Distributed sensing technology has progressed to the point, where it is being tested on aircraft such as Ikhana and the upcoming X-56A. Previously, the modal filter was criticized for requiring too many sensors. It was never assessed for its potential benefits in aircraft control. Therefore it is of practical interest to reinvestigate the modal filter. The first case study shows that under conditions of sensor normality, the modal filter is a Gaussian efficient estimator in an aeroservoelastic environment. This is a fundamental experiment considering the fact that the modal filter has never been tested in the airflow. To perform this case study a linear aeroservoelastic code capable of modeling distributed sensing is developed and experimentally validated. From this code, a computational wing model is fitted with distributed sensing. A modal filtering design methodology is developed and applied. With distributed sensing and modal filtering feedback control is achieved. This is also compared and contrasted with a controller using state-of-the-art accelerometers. In addition, new methods of active shape control are introduced for warping an aeroelastic structure utilizing the modal filter and control surfaces. The next case study takes place in a realistic setting for an aircraft. Flexible aircraft bring challenges to the active control community. Increased gust loads, possibility of flutter, and off-design drag may detrimentally affect performance and safety. Aeroservoelastic tailoring, gust load alleviation (GLA) and active flutter suppression (AFS) may be required on future flexible air vehicles. It is found that modal filters can theoretically support these systems. The aircraft case study identifies additional steps required in the modal filtering design methodology. Distributed sensing, the modal filter and modal reference shape control are demonstrated on the X-56A flutter-unstable simulation model. It is shown that control of deformations at potentially millions of points on an aircraft vehicle can be achieved through control of a few modal coordinates. Finally modal filter robustness is theoretically improved and computationally verified. State-of-the-art modal filters have high bias sensitivity. In fact, this is so critical that state-of-the-art modal filters may never be certified for aircraft implementation. This is especially true within a flight critical control system. The solution to this problem is found through derivation of the robust modal filter. The filter combines good properties of concentration algorithms with robust re-descending M-estimation. A new trim criterion specific to the strain based modal sensing system is derived making the filter robust to asymmetric or leverage point outliers. Robust starts are introduced to improve convergence of the modal estimation system to the globally optimal solution in the presence of 100s of biased fiber optic sensors.

To meet the economic, social and infrastructure needs of the community for safe and efficient transportation systems, long span bridges have been built throughout the world. Long span bridges are one of the most challenging kinds of structures in civil engineering. The cable-stayed bridges are of great interest mainly as an alternative and a more economic solution than the one of suspension bridges. In addition, the fiber reinforced polymer (FRP) composites are, nowadays, successfully used for constructing modern bridges, where the significant weight saving provides additional benefits. Because of the great flexibility, modern long-span cable-stayed bridges are usually very susceptible to dynamic loads especially to the earthquake and strong winds. Therefore, the earthquake-resistant and wind-resistant designs become one of key issues for successful construction of bridges. The objective of the present research is to develop a very efficient spline finite strip technique, for modelling and analysis of both conventional and hybrid FRP cable-stayed bridges. The study falls into the categories of bending, free vibration, seismic, and aerodynamic flutter analysis. The spline finite strip method (SFSM) is one of the most efficient numerical methods for structural analysis of bridges, reducing the time required for estimating the structural response without affecting the degree of accuracy. In the finite strip method, the degrees of freedom could be significantly reduced due to the semi-analytical nature of this method. However, the previous versions of SFSM are not able to model the entire bridge system. For that reason, the structural interactions between different structural components of the bridge could not be handled. In addition, the vibrations and displacements of the towers and cables could not be investigated. In the present formulation, all these obstacles have been eliminated. Moreover, the proposed finite strip technique is very efficient and accurate due to the drastic reduction in the formulation time, simplicity of data preparation, rapid rate convergence of the results, and the semi-analytical nature. Last but not least, and for the first time, a fully finite strip solution is extended to the area of wind engineering. Using the spline finite strip discretization, the aerodynamic stiffness and mass properties of the long-span cable-stayed bridge are derived. The aerodynamic properties along with the structural properties of long-span plates and bridges are formulated in the aerodynamic equation of motion and are used to analyze the flutter problem. The accuracy and efficiency of the proposed advanced finite strip method is verified against the finite element and field measurement results. The results demonstrate that this methodology and the associated computer code can accurately predict the dynamic and aerodynamic responses of the conventional and FRP long-span cable-stayed bridge systems. The outcome of the present research will lead to a comprehensive structural analysis of bridges in the framework of the proposed discretization which is more efficient and straightforward than the finite element analysis.

Dans la conception des turbomachines modernes, la prédiction des phénomènes aéroélastiques est devenue un point clé. La tendance à réduire la masse et à augmenter la charge des composants aérodynamiques accroit le risque de rupture. Dans un tel contexte, la compréhension et la bonne prédiction des diverses instabilités constituent un enjeu industriel et scientifique majeur. Le présent travail de recherche a pour objectif d’améliorer la prédiction des phénomènes instationnaires intervenant dans les problèmes d’aéroélasticité en turbomachines. Cette thèse est plus particulièrement axée sur la simulation de l’interaction onde de choc/couche limite. Le support d’étude est une tuyère transsonique présentant un écoulement avec des zones décollées. L’oscillation forcée de l’onde de choc est simulée grâce à une méthode de petites perturbations instationnaires couplée avec une hypothèse de turbulence variable. Cette approche est validée par comparaison avec des mesures. Elle permet une prédiction tout à fait satisfaisante du premier harmonique de pression sur la paroi de la tuyère. Ce travail a montré la nécessité de linéariser le modèle de turbulence. Le besoin de dériver le modèle de turbulence nous a amené à investiguer la modélisation faite pour prédire l’interaction onde de choc/couche limite. Un modèle de turbulence à deux équations complété par une équation de « retard » est implémenté afin de capter un déséquilibre de la turbulence. Les résultats obtenus en tuyère sont cohérents avec la théorie mais une surproduction d’énergie turbulente en présence de bord d’attaque rend le modèle inefficace pour des configurations de turbomachines. Au final, l’introduction d’un limiteur de viscosité turbulente dans un modèle de turbulence à deux équations s’avère donner de bons résultats. La méthode de dérivation du modèle est alors présentée sur le modèle de Wilcox proposé en 2008. Enfin, la technique de linéarisation est étendue à la problématique aéroélastique. Une approche de couplage fluide-structure faible est adoptée. L’oscillation structurelle des aubages suivant les modes propres est considérée mais en laissant la fréquence évoluer au cours du couplage. La nouvelle méthode utilisée s’appuie sur la construction d’un méta-modèle du comportement dynamique du fluide afin de résoudre directement le système fluide-structure couplé. Cette technique est validée sur une configuration de grille annulaire de turbine en haut subsonique et présente l’avantage d’un temps de calcul réduit. / In modern turbomachinery design, predicting aerolastic phenomena has become a key point. The development of highly loaded components, while reducing their weight, increases the risk of failure. In this context, good understanding and prediction of various instabilities are a major industrial and scientific challenge. This research work aims to improve the prediction of unsteady phenomena involved in turbomachinery aeroelasticity. This study focuses especially on the simulation of shock wave/boundary layer interaction. To begin with, a transonic nozzle separated flow is investigated. Forced oscillation of the shock wave system is simulated through a small unsteady perturbation method combined with the assumption of variable turbulence. This approach is validated against exprimental measurements. The first harmonic of pressure on the wall of the nozzle is predicted quite satisfactorily. The need to linearize the turbulence model was shown of high importance. Deriving the turbulence model, leads us to investigate the turbulence modeling performed to predict the shockwave/boundary layer interaction. A two equations turbulence model supplemented by a "time-lagged" equation is implemented to capture non-equilibrium effects of turbulence. All achieved results for a nozzle are consistent with theory, but overproduction of turbulent kinetic energy at leading edge makes the model useless for turbomachinery configurations. However, the introduction of an eddy viscosity stress limiter inside a two-equation turbulence model proves to give good results. The derivation method is thus presented on such a model, precisely on Wilcox model proposed in 2008. Finally, the linearization technique is extended to aeroelastic problems. A loose fluid-structure coupling strategy is adopted. The structural oscillation of the blades is considered for eigen-modes but frequency is free to change during coupling resolution. The new approach is based on the building of a meta-model to describe the fluid dynamic behavior in order to solve directly the coupled fluid-structure system. This technique is validated on a standard high subsonic turbine configuration and takes advantage of a reduced computation time.

Cette thèse est consacrée à l'étude d'amortisseurs passifs non linéaires innovants pour le contrôle de l'instabilité de flottement sur un profil d'aile à deux degrés de libertés. Lorsqu'un profil d'aile entre en flottement, il oscille de façon croissante jusqu'à se stabiliser sur un cycle limite dont l'amplitude peut être significative et détériorer sa structure. Le contrôle a ainsi deux objectifs principaux : retarder l'apparition de l'instabilité et réduire l'amplitude des cycles limites. Avant d'étudier l'influence des amortisseurs passifs, l'instabilité de flottement, et notamment le régime post-flottement, a été étudié. Une expérience de flottement sur une plaque plane a été menée et sa modélisation, prenant en compte le phénomène de décrochage dynamique, a été réalisée. Concernant le contrôle passif, le premier type d'amortisseur étudié est un amortisseur hystérétique réalisé à l'aide de ressorts en alliage à mémoire de forme. La caractéristique principale de tels amortisseurs est que leur force de rappel étant hystérétique, elle permet de dissiper une grande quantité d'énergie. L'objectif principal est ainsi de réduire l'amplitude des cycles limites provoqués par l'instabilité de flottement. Cet effet escompté a été observé et quantifié expérimentalement et numériquement à l'aide de modèles semi-empiriques. Le second type d'amortisseur utilisé est un amortisseur non linéaire de vibration accordé. Il est composé d'une petite masse connectée au profil d'aile à l'aide d'un ressort possédant une raideur linéaire et une raideur cubique. La partie linéaire de ce type d'amortisseur permet de retarder l'apparition de l'instabilité tandis que la partie non linéaire permet de réduire l'amplitude des cycles limites. L'influence de l'amortisseur non linéaire de vibration accordé a été étudiée analytiquement et numériquement. Il a été trouvé que l'apparition de l'instabilité est significativement retardée à l'aide de cet amortisseur, l'effet sur l'amplitude des cycles limites étant plus modeste. / The aim of this thesis is to study the effect of passive nonlinear absorbers on the two degrees of freedom airfoil flutter. When an airfoil is subject to flutter instability, it oscillates increasingly until stabilizing on a limit cycle, the amplitude of which can be possibly substantial and thus damage the airfoil structure. The control has two main objectives : delay the instability and decrease the limit cycle amplitude. The flutter instability, and the post-flutter regime in particular, were studied first. A flutter experiment on a flat plate airfoil was conducted and the airfoil behavior was modeled, taking into account dynamic stall. Regarding the passive control, the first absorber studied was a hysteretic damper, realized using shape memory alloys springs. The characteristic of such dampers is their hysteretic restoring force, allowing them to dissipate a large amount of energy. Their main goal was thus to decrease the limit cycle amplitude caused by the flutter instability. This expected effect was observed and quantified both experimentally and numerically, using heuristic model. The second absorber studied was a nonlinear tuned vibration absorber. This absorber consists of a light mass attached to the airfoil through a spring having both a linear and a cubic stiffness. The role of the linear part of such absorber was to repel the instability threshold, while the aim of the nonlinear part was to decrease the limit cycle amplitude. It was found, analytically and numerically, that the instability threshold is substantially shifted by this absorber, whereas the limit cycle amplitude decrease is relatively modest.

Aeroelasticita je nezbytná vědní disciplína zahrnuta do návrhu letounů. Zaměřuje se na předpovídání jevů, které vznikají vlivem interakce aerodynamických, elastických a setrvačných sil. Tyto jevy často vedou ke katastrofickým následkům, proto musí být prokázáno, že nevzniknou v rozsahu rychlostí ohraničujících letovou obálku. Aplikace moderních materiálů při konstrukci draku, spolu se snahou navrhnout aerodynamicky efektivní tvar křídel, vede ke zvyšování poddajnosti letounů. To má za následek změnu aerodynamických vlastností a také k výraznějšímu vliv na aeroelastické jevy, které mohou být vyvolány snadněji vlivem pohybů tuhého tělesa než v případě tužších konstrukcí. Aeroelastické jevy mohou vznikat v širokém rozsahu rychlostí zahrnujícím i transsonickou oblast. V této oblasti je ovlivněna zejména rychlost, při níž dochází k třepetání, a to vlivem nelineárních jevů v proudu. Běžné nástroje, které jsou založeny na lineárních teoriích, nejsou schopny tyto nelineární jevy popsat. Cílem práce je proto navrhnout, implementovat a otestovat nástroj pro výpočetní (numerickou) simulaci aeroelasticity. Nástroj má využívat řešič proudového pole, který je schopen předpovědět nelineární jevy. V práci je kladen důraz na simulaci statické aeroelasticity. V práci jsou popsány metody, které je nutno zahrnout do numerické simulace statické aeroelasticity. Dále je popsán vlastní nástroj a je provedeno zhodnocení konvergence statických aeroelastických výpočtů. Funkčnost nástroje byla ověřena na příkladech, kdy byly použity různé aerodynamické a strukturální modely. Nástroj byl také aplikován při aerodynamické tvarové optimalizaci poddajného křídla. Výsledky optimalizace a její výpočetní náročnost byly porovnány s případem optimalizace tuhého křídla. Na závěr je v práci prezentován příspěvek autora do výzkumu zaměřeného na zhodnocení vlivu časové synchronizace mezi CFD a CSM řešiči. Použitý testovací případ je transsonické obtékání křídla na začátku třepetání (flutteru). Výsledky byly srovnány s experimentálními daty poskytnutými NASA.

Title: Dependence of the air consumption and the position of the body on the selected method of diving kick and swimming speed Objectives: The goal of this work is to find out the relationship between the diver's swimming speed and the air consumption while using two different methods of diving kicks - flutter and frog kick. At the same time, assess the dependence of the position of the body and head on the swimming speed and method of diving kicks. Methods: In this work was used method of collecting data in real conditions by measuring devices and statistical evaluation of collected data. Results: The results are presented by graphs both in the text of this work and in attachment for its large size. The results of all probands are presented in summary graphs and for selected values the degree of association is calculated in tables using the Pearson correlation coefficient. The main result is the confirmation of the reduction of the deviation from the horizontal position when comparing the slow and higher swimming speeds of both flutter and frog kick. The most effective way for a diver to overcome 50 meters below the water surface was determined to be a flutter kick at medium speed (average 0,37 m/s). Keywords: scuba diving, body position, head position, air consumption, speed of swimming, flutter...

Modeling is an essential discipline that is especially important in the field of software engineering. Students and developers alike employ models to describe systems on an abstract level, capture requirements, and communicate with other teams. For that purpose, UML diagrams are usually the instrument of choice. Over the course of the last decade, mobile devices increased in prevalence and popularity and flexible work arrangements were introduced in a larger number of workplaces. Effective collaboration is more important than ever. However, the tools have not kept up with these developments. There exists no semantics-aware mobile modeling application that supports collaboration in real time, a gap in the market. This thesis investigates existing applications in the mobile modeling space and their shortcomings, technologies for developing cross-platform apps, and methodologies for facilitating conflict-free collaboration. Based on the findings, it conceptualizes and implements CoMod, a proof of concept allowing users to collaboratively edit UML class diagrams in real time. The system consists of a Flutter-based client application for Android and iOS and a Node.js-based server executable. These components utilize conflict-free replicated data types (CRDTs) to merge participants' changes and communicate via WebSocket connections. Moreover, CoMod's feasibility is evaluated by means of a case study investigating the system's scalability and performance characteristics. It has been shown that CoMod is able to handle common use cases arising in software engineering teams or group projects at university. It is further kept sufficiently general to allow other types of models to be supported without having to alter the entire system.:1 Introduction 1.1 Requirements 1.2 Problem Description 1.3 Objectives 1.4 Structure 2 Background 2.1 Software Modeling 2.1.1 Unified Modeling Language 2.2 Cross-Platform Application Development 2.2.1 Web Apps 2.2.2 Hybrid Apps 2.2.3 Native cross-platform apps 2.2.4 Summary 2.3 Real-Time Collaboration 2.3.1 Conflict-Free Replicated Data Types (CRDTs) 2.3.2 Operational Transformation 3 Related Work 3.1 Astah UML 3.2 Lucidchart 3.3 System Designer 3.4 Summary 4 Concept 4.1 Objectives 4.2 User Interface 4.3 Data Model 4.4 Collaboration 4.4.1 Conflict handling 4.4.2 System architecture 4.4.3 Client-server communication 4.5 Summary 5 Solution 5.1 Client 5.1.1 Walkthrough 5.1.2 Data model 5.1.3 JavaScript subsystem 5.1.4 Dependencies 5.2 Server 5.2.1 Dependencies 5.3 Collaboration 5.3.1 Client-server communication 5.3.2 Client data flow 5.4 Testing 5.4.1 Unit tests 5.4.2 Integration tests 5.4.3 End-to-end tests 5.5 Extensibility 6 Evaluation 6.1 Case Study 6.2 Technical Analysis 6.2.1 Test data generator 6.2.2 Client analysis 6.2.3 Server analysis 6.3 Threats to Validity 7 Conclusion 7.1 Fulfillment of Objectives 7.2 Future Work Acronyms Bibliography

La déflection statique d'une structure flexible exposée à un écoulement transverse permet classiquement de réduire la traînée à laquelle elle est soumise. Dans le domaine de la biomécanique, la déformation induite par l'écoulement d'éléments végétaux flexibles conduisant à une réduction du chargement est désignée par le terme `reconfiguration' pour souligner le caractère avantageux de ce processus adaptatif. Dans cette thèse, nous examinons les mécanismes qui sous-tendent le processus de reconfiguration, dans des systèmes fluide-structure présentant une variabilité spatiale, ou de la dynamique provenant au choix de l'instationnarité de l'écoulement de base, d'un couplage fluide-structure conduisant à une instabilité, ou de vibrations induites par vortex. Nous montrons que l'aptitude des structures flexibles à réduire l'intensité du chargement imposé par l'écoulement est preservée en présence de non-uniformités ou de dynamique, à condition que le design de la structure soit tel que la traînée résistive domine les forces inertiels. Nous montrons de plus que la capacité à se déformer présente l'avantage supplémentaire de permettre la réduction des vibrations induites par vortex. Notre travail indique également que des structures légères et élancées sont les mieux adaptées pour supporter les chargements induits par l'écoulement en se reconfigurant, et que l'efficacité de la réduction du chargement par reconfiguration élastique dépend faiblement de la distribution spatiale des propriétés du système. Finalement, la réduction des chargements résulte toujours, indépendamment du régime de reconfiguration, de la concentration de la déformation sur une longueur caractéristique inférieure à la longueur réelle de la structure. / The static deflection of a flexible structure exposed to a transverse flow is classically known to reduce the drag it has to withstand. In the field of biomechanics, the flow-induced deformation of flexible plant elements leading to a reduction of the loads is referred to as `reconfiguration', in order to highlight the alleged benefits of such adaptive process. In this thesis, we investigate the mechanisms underpinning the reconfiguration in flow-structure systems featuring some spatial variability, or some dynamics arising either from the unsteadiness of the free-stream, from a flow-structure coupling leading to an instability, or from vortex-induced vibrations. We show that the ability of flexible structures to reduce the magnitude of the flow-induced loads is preserved in the presence of non-uniformities or dynamics, provided that the design of the structure is such that resistive drag dominates over inertial forces. We also show that the ability to deform has the added benefit of reducing the magnitude of the vortex-induced vibrations. Our work further indicates that light, slender structures are better suited to accommodate the flow-induced loads by reconfiguring, and that the efficiency of the process of load reduction by elastic reconfiguration is weakly sensitive to the spatial distribution of the system properties. Finally, regardless of the regime of reconfiguration, the reduction of the load always results from the concentration of the deformation on a characteristic bending length smaller than the actual length of the structure.

Cross-platform frameworks enable development for multiple platforms, such as iOS and Android, using the same codebase. Evaluation of cross-platform frameworks has traditionally been geared towards technical assessments and, more seldom, targeted usability, leaving a gap to be explored. This paper presents a usability analysis of Flutter and React Native, supported by a user study using the Cognitive Dimensions of Notations framework (CDN framework). Six developers were recruited and interviewed with the CDN framework questionnaire and a thematic analysis was performed where several usability issues, benefits and design trade-offs were identified. A recurring topic amongst the React Native developers was issues regarding hooks, while the Flutter developers unanimously identified problems relating to layout design. React Native was highlighted for its abstraction and progressive evaluation capabilities, indicating an edge toward Flutter. In contrast, comments regarding Flutters tooling capabilities and UI libraries showed an edge towards React Native. The identified usability benefits and trade-off characteristics give insight into each framework’s strengths and weaknesses. / “Cross-platform”-ramverk möjliggör applikationsutveckling till ett flertal plattformar såsom iOS och Android genom användning av samma kodbas. Flutter och React Native är i dagsläget två av de mest eftersökta “cross-platform”-ramverken. Utvärdering av dessa ramverk har vanligtvis utvärderat den tekniska aspekten, och mer sällan fokuserat på användbarhet. Denna masteruppsats presenterar en användbarhetsanalys av Flutter och React Native genom en användarstudie med utgångpunkt i ramverket “Cognitive Dimensions of Notations” (CDN-ramverket). Sex utvecklare rekryterades och intervjuades genom ett formulär tillhörande CDN-ramverket. En tematisk analys genomfördes på den insamlade datan och identifierade ett flertal problem och överväganden gällande design. Ett återkommande tema bland React Native-utvecklarna var problem relaterat till “hooks” medan Flutter-utvecklarna beskrev problem avseende layout-design. React Native mottog positiva kommentarer relaterat till abstraktionkapacitet och progressiv utvärdering jämfört med Flutter. Flutter mottog positiv kritik angående verktyg samt tillhörande UI-bibliotek jämfört med React Native. Utvärderingen av Flutter och React Native ger insyn i respektive ramverks styrkor och svagheter.