Welds play a crucial role in the product portfolio of GKN Aerospace. For ease of manufacturing and repairability, butt welds are preferred in the aerospace industry. Weld regions undergo local distortions during manufacturing due to the external heat-input, and the resulting local geometries are complex and stochastic in nature. Under operational loads, the distorted geometry affects the local stress field around the weld region, and this has a significant impact on the fatigue life. Traditional design calculations of welds resort to idealization of the local weld geometry. In this thesis, the influence of real weld geometry on the computed fatigue life is investigated. Linear elastic fracture mechanics principles are utilized to calculate the fatigue life of a weld starting from a pre-defined initial crack. The influence of important weld geometric parameters, namely, – edge offset and weld toe radii, on the fatigue life is investigated in detail. A statistical analysis approach, using transfer functions and Monte Carlo simulation, is devised to study the effect of variation in the different weld geometric parameters. Different edge offset measures from a real geometry are identified and these measures are investigated as potential candidates to obtain conservative life estimates using the idealized geometry. Investigations in this thesis show that the real geometry has a significant effect on the weld fatigue life. In all cases of local weld geometry, the edge offset has the largest influence on life. For a real weld geometry, the root toe radius has a significant influence on life. In an idealized geometry, for the same normalized edge offset, an increase in the plate thickness leads to a decrease in life. A new edge offset measure is proposed that leads to conservative life estimates when used in conjunction with the idealized geometry, thus enabling computationally efficient design calculations. / Svetsar spelar en avgörande roll i GKN Aerospace produktportfölj. För att underlätta vid tillverkning och reparationer föredras stumsvetsar inom flygindustrin. Svetsområden genomgår lokala deformationer under tillverkningen på grund av extern värmepåverkan, och de resulterande lokala geometrierna är komplexa och stokastiska till sin natur. Vid termisk och mekanisk belastning i drift påverkar den deformerade geometrin det lokala spänningsfältet runt svetsområdet vilket har en betydande inverkan på utmattningslivslängden. Vid traditionell dimensionering av svetsar idealiseras den lokala svetsgeometrin. Denna avhandling undersöker inverkan av verklig svetsgeometri på den beräknade utmattningslivslängden. Linjärelastisk brottmekanik används för att beräkna utmattningslivslängden för en svets med utgångspunkt från en fördefinierad initial spricka. Inverkan av viktiga svetsgeometriska parametrar, nämligen - kantförskjutning och svetsradie, på utmattningslivslängden undersöks i detalj. En statistisk analysmetod, med hjälp av överföringsfunktioner och Monte Carlo simulering, är framtagen för att studera effekten av variation i de olika svetsgeometriska parametrarna. Olika kantförskjutningsmått från en verklig geometri identifieras och dessa mått undersöks som potentiella kandidater för att erhålla konservativa livslängdsuppskattningar med hjälp av den idealiserade geometrin. Undersökningar i denna avhandling visar att den verkliga geometrin har en signifikant effekt på svetsutmattningslivslängden. I alla fall av lokal svetsgeometri har kantförskjutningen den största inverkan på livslängden. För en riktig svetsgeometri har svetsradien vid svetsens rotsida en betydande inverkan på livet. I en idealiserad geometri, för samma normaliserade kantförskjutning, leder en ökning av plåttjockleken till en minskning av livslängden. Ett nytt kantförskjutningsmått föreslås som leder till konservativa livslängdsuppskattningar när de används i kombination med den idealiserade geometrin, vilket möjliggör beräkningseffektiva designberäkningar.

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Thèse réalisée en cotutelle entre l'Université de Montréal et l'Université Bourgogne Franche-Comté / Les feux, le climat et leurs interactions sont des facteurs clés de la dynamique des forêts boréales. Dans un contexte où les changements climatiques en cours augmentent les risques d’incendies, une hausse de la fréquence des feux constitue une menace pour les populations locales (qualité de l’air, risques sanitaires, décès, etc.), les ressources forestières (déforestation, baisse de volume bois, etc.) et l’environnement (perte d’habitats naturels, hausse des émissions de CO2, pollution diverse, etc.). Comprendre les dynamiques passées aidera à gérer durablement les forêts boréales et à anticiper les effets des changements climatiques futurs. A l'aide d’analyses paléoécologiques multiproxies (chironomes, charbon de bois, pollen) de trois carottes sédimentaires (lacs Mista et Adèle (est du Québec), Aurélie (Ouest du Québec)), nous avons documenté les interactions à long terme entre le climat, le feu et la végétation le long d’un gradient longitudinal est-ouest du Québec au cours des 8500 dernières années. Nos résultats suggèrent l'existence d'un fort contraste de températures estivales entre l'est et l'ouest du Québec avant 7000 ans AA (avant l’actuel). Dans l'est, durant cette période, l'influence indirecte des vestiges de l'Inlandsis Laurentidien et les conditions de surface de l'océan contrebalancent l'insolation maximale pour induire des conditions estivales plus fraîches. La température estivale maximale n'est atteinte qu'entre 6000 et 5000 ans AA. L'ouest du Québec est peu ou pas affecté par ces influences et l'évolution des températures semble parallèle à la diminution de l'insolation pendant l'été, avec un maximum de températures autour de 7500 ans AA. Les changements de températures estivales ne semblent pas jouer un rôle prépondérant sur la dynamique de la végétation et des feux à l’est du Québec. La dynamique à long terme de la pessière à mousses de l’est est contrôlée, entre autres, par la taille et la fréquence des feux. Au lac Adèle, la pessière à mousses s'est ouverte vers 3000 ans AA. Mais le seuil de résilience de Picea mariana a probablement été dépassé vers 1500 ans AA, conduisant à la transformation de la pessière à mousses en pessière à lichens. Des incendies récurrents à intervalles rapprochés semblent être le principal mécanisme de déclenchement. Au lac Mista, la pessière à mousses s'est ouverte vers 2000 ans AA, mais elle s’est probablement redensifiée au cours des 300 dernières années. Bien que la pessière à mousses semble résiliente, elle reste dans un état d'équilibre précaire car la fréquence des incendies pourrait augmenter dans le contexte du changement climatique et déclencher la transformation de la pessière à mousses en pessière à lichens. A l’opposé des sites à l’est du Québec, à Aurélie (ouest du Québec), les feux semblent moins récurrents avec le refroidissement de la température estivale. Il existe une relation entre les variations de température estivale et la végétation. Il y a donc un contraste entre l’est et l’ouest sur les processus de contrôle de la dynamique de la végétation. / Fire, climate and their interactions are key factors in the dynamics of boreal forests. In a context where the ongoing climate change is increasing fire risk, a rise in fire frequency poses a threat to local populations (air quality, health risks, deaths, etc.), forest resources (deforestation, drop in timber volume, etc.) and the environment (loss of natural habitats, rise in CO2 emissions, various types of pollution, etc.). Understanding past dynamics will help to manage boreal forests sustainably and anticipate the effects of future climate change. Using multiproxy paleoecological analyses (chironomids, charcoal, pollen) of three sediment cores (lakes Mista and Adèle (eastern Quebec), Aurélie (western Quebec)), we have documented the long-term interactions between climate, fire and vegetation along a longitudinal east-west gradient in Quebec over the past 8500 years. Our results suggest the existence of a strong contrast in summer temperature between eastern and western Quebec prior to 7000 years BP (before present). In the east, during this period, the indirect influence of the remnants of the Laurentide Ice Sheet and ocean surface conditions offset maximum insolation to induce cooler summer conditions. Maximum summer temperatures were only reached between 6000 and 5000 cal yr BP. Western Quebec is little or unaffected by these influences, and the evolution of temperatures parallels the decrease in insolation during summer, with a temperature maximum around 7500 cal yr BP. Changes in summer temperatures are probably not the main factor controlling fire and vegetation dynamics in eastern Quebec. The long-term dynamic of the eastern spruce-moss forest is controlled, among other things, by the size and frequency of fires. At Lake Adèle, the spruce-moss forest opened around 3000 cal yr BP. But the resilience threshold of Picea mariana was probably exceeded around 1500 cal yr BP, leading to the transformation of the spruce-moss forest into a lichen woodland. Recurrent fires at short intervals seem to be the main triggering mechanism. At Lake Mista, the moss forest opened around 2000 cal yr BP, but has probably redensified over the last 300 years. Although the spruce-moss forest seems resilient, it remains in a precarious state of equilibrium, as the frequency of fires could increase in the context of climate change, triggering the transformation of the spruce-moss forest into a lichen woodland. In contrast to the sites in eastern Quebec, in Aurélie (western Quebec), fires seem to recur less frequently as summer temperatures cool. There is a relationship between summer temperature variations and vegetation. There is therefore a contrast between east and west in terms of the processes controlling vegetation dynamics.

<p dir="ltr">The proliferation of internet-connected embedded devices in contemporary computing environments has raised significant concerns regarding data security and confidentiality. Most embedded devices rely on computationally secure cryptographic algorithms to address these imperatives. However, despite the mathematical assurances, the physical implementation of these algorithms introduces vulnerabilities. Specifically, side-channel analysis (SCA) attacks exploit information leakage through various channels, including power consumption, electromagnetic (EM) radiation, timing, cache hits and misses, and other observable characteristics. </p><p dir="ltr">Previous research has introduced the concept of attenuating information-sensitive signatures using an analog cascoded current source for power delivery, coupled with an analog biased PMOS-based local negative feedback mechanism to stabilize the internal node. While this approach achieves robust signature suppression, resulting in higher minimum traces to disclosure (MTD) and enhanced security, it remains limited by its analog nature, making it less adaptable across different technology nodes. This thesis proposes a digital-friendly signature suppression technique that employs a digital cascoded current source and leverages a Ring-oscillator-based bleed path. These digital countermeasures can be further enhanced through time-domain obfuscation techniques. Our work demonstrates a state-of-the-art MTD of 1.25 billion traces for an AES-256 implementation. However, these countermeasures lack provable security guarantees, so continuous stress testing is essential for widespread deployment. Different intelligent attacks can be exploited on these physical countermeasures. Notably, this thesis also presents an intelligent attack on signature attenuation-based physical countermeasures and introduces an attack detector. Developing an intelligent attack detector is an integral part of the commercial adoption of physical countermeasures. </p><p dir="ltr">Next, generic physical countermeasures are often deployed in the $V_{DD}$ port as power side channel analysis is carried out through the $V_{DD}$ port. However, any digital circuit has two standard ports, namely $V_{DD}$ and clock port, and countermeasure through the clock port is mainly unexplored except for the system-level clock randomization technique. Even the clock-randomization technique is rendered ineffective in the presence of post-processing techniques. This thesis introduces a side channel resilience technique by introducing a larger slew at the clock, thereby improving MTD by $100\times$.</p><p dir="ltr">Next, these physical countermeasures do not come with any provable security guarantee. Hence, it is important to stress-test the countermeasures. This thesis does so and finds an exploitable point to reduce MTD by 1000$\times$. An attack detector of such an attack is also proposed.</p><p dir="ltr">Further, an attack detection strategy against side-channel analysis (SCA) or fault injection attacks (FIA) is also required. A detection and mitigation approach often gives us the option of duty-cycled countermeasures, hence reducing the energy overhead. This thesis proposes and analyzes a self-aware inductive loop-based attack detection strategy to detect SCA and FIA and enhance the signature attenuation countermeasures. </p><p dir="ltr">Finally, we explore opportunities for integrating these lightweight generic techniques into recently standardized Post-Quantum Cryptographic (PQC) cores. Specifically, we present an optimized implementation of the Saber PQC core, a NIST standardization finalist, achieving the lowest area and energy consumption. Future work could involve deploying lightweight PQC cores with synthesizable physical countermeasures to enhance security against quantum algorithms and physical side-channel attacks.</p>

This dissertation presents research in the development and use of a multi-modal visual and haptic virtual model in higher education. The model, named Chemical Force Feedback (CFF), represents molecular recognition through the example of protein-ligand docking, and enables students to simultaneously see and feel representations of the protein and ligand molecules and their force interactions. The research efforts have been divided between educational research aspects and development of haptic feedback techniques. The CFF model was evaluated in situ through multiple data-collections in a university course on molecular interactions. To isolate possible influences of haptics on learning, half of the students ran CFF with haptics, and the others used the equipment with force feedback disabled. Pre- and post-tests showed a significant learning gain for all students. A particular influence of haptics was found on students reasoning, discovered through an open-ended written probe where students' responses contained elaborate descriptions of the molecular recognition process. Students' interactions with the system were analyzed using customized information visualization tools. Analysis revealed differences between the groups, for example, in their use of visual representations on offer, and in how they moved the ligand molecule. Differences in representational and interactive behaviours showed relationships with aspects of the learning outcomes. The CFF model was improved in an iterative evaluation and development process. A focus was placed on force model design, where one significant challenge was in conveying information from data with large force differences, ranging from very weak interactions to extreme forces generated when atoms collide. Therefore, a History Dependent Transfer Function (HDTF) was designed which adapts the translation of forces derived from the data to output forces according to the properties of the recently derived forces. Evaluation revealed that the HDTF improves the ability to haptically detect features in volumetric data with large force ranges. To further enable force models with high fidelity, an investigation was conducted to determine the perceptual Just Noticeable Difference (JND) in force for detection of interfaces between features in volumetric data. Results showed that JNDs vary depending on the magnitude of the forces in the volume and depending on where in the workspace the data is presented.

Approved for public release, distribution is unlimited / In this thesis, the ocean was modeled as a waveguide with an ideal pressure - release surface, and an ideal rigid bottom. The ocean waveguide was then treated as a linear, time - invariant, space - variant (TISV) filter or communication channel. The filter is time - invariant because no motion was modeled and because the properties of the ocean were assumed to be constant. The filter is space - variant because of the presence of the two boundaries, that is, the ocean surface and ocean bottom. This thesis investigates the ocean as a linear TISV filter by evaluating 1) the complex frequency response, 2) the impulse response, and 3) the transfer function of the ocean with respect to depth. It is shown that the TISV impulse response of the ocean contains information that can be used to help localize a target in range and whether the target is above or below the receiver. Computer simulation results were obtained by evaluating the three filter functions for several different test cases. / Ensign, United States Navy

Esta tese examina o problema de detecção de conectividade entre séries temporais no sentido de Granger no caso em que a natureza não linear das interações não permite sua determinação por meio de modelos auto-regressivos lineares vetoriais. Mostra-se que é possível realizar esta detecção com auxílio dos chamados métodos de Kernel, que se tornaram populares em aprendizado por máquina (\'machine learning\') já que tais métodos permitem definir formas generalizadas de teste de Granger, coerência parcial direcionada e função de transferência direcionada. Usando simulações, mostram-se alguns exemplos de detecção nos quais fica também evidente que resultados assintóticos deduzidos originalmente para estimadores lineares podem ser generalizados de modo análogo, mostrando-se válidos no presente contexto kernelizado. / This work examines the connectivity detection problem between time series in the Granger sense when the nonlinear nature of interactions determination is impossible via linear vector autoregressive models, but is, nonetheless, feasible with the aid of the so-called Kernel methods that are popular in machine learning. The kernelization approach allows defining generalised versions for Granger tests, partial directed coherence and directed transfer function, which the simulation of some examples shows that the asymptotic detection results originally deducted for linear estimators, can also be employed under kernelization if suitably adapted.

Ziel dieser Arbeit ist es eine Beziehung zwischen den biophysikalischen Eigenschaften der Nervenmembran, und den ausgeführten Berechnungen und Filtereigenschaften eines tonisch feuernden Neurons, unter Einbeziehen intrinsischer Fluktuationen, herzustellen. Zu diesem Zweck werden zu erst die mikroskopischen Fluktuationen, die durch das stochastische Öffnen und Schließen der Ionenkanäle verursacht werden, zu makroskopischer Varibilität in den Zeitpunkten des Auftretens der Aktionspotentiale übersetzt, denn es sind diese Spikezeiten die in vielen sensorischen Systemen informationstragenden sind. Die Methode erlaubt es das stochastischer Verhalten komplizierter Ionenkanalstrukturen mit einer großen Zahl an Untereinheiten, in Spikezeitenvariabilität zu übersetzen. Als weiteres werden die Filtereigenschaften der Nervenzellen in der überschwelligen Dynamik, also bei Existenz eines stabilen Grenzzyklus, aus ihren Phasenantwortkurven (PAK), einer Eigenschaft des linearisierten adjungierten Flusses auf dem Grenzzyklus, in einem stöhrungstheoretischen Ansatz berechnet. Es ergibt sich, dass Charakteristika des Filter, wie beispielsweise die DC Komponente und die Eigenschaften des Filters um die Fundamentalfrequenz und ihrer Harmonien, von den Fourierkomponenten der PAK abhängen. Unter Verwendung der hergeleiteten Filter und weiterer Annahmen ist es möglich das frequenzabhängige Signal-zu-Rauschen Verhältnis zu berechnen, und damit eine untere Schranke für die Informationstransferrate eines Leitfähigkeitsmodells zu berechnen. Unter Zuhilfenahme der numerischen Kontinuierungsmethode ist es möglich die Veränderungen in der Spikevariabilität und den Filtern für jeden biophysikalischen Parameter des System zu verfolgen. Weiterhin wurde die verwendete Phasenreduktion durch eine Korrektur ergänzt, die die Radialdynamik einbezieht. Es zeigt sich, dass die Krümmung der Isochronen einen Einfluss darauf hat ob das Rauschen einen positiven oder negativen Frequenzschift hervorruft. / The goal of the thesis is to establish quantitative, analytical relations between the biophysical properties of nerve membranes and the performed neuronal computations for neurons in a tonically spiking regime and in the presence of intrinsic noise. For this purpose, two major lines of investigation are followed. Firstly, microscopic noise caused by the stochastic opening and closing of ion channels is mapped to the macroscopic spike jitter that affects neural coding. The method is generic enough to allow one to treat Markov channel models with complicated, high-dimensional state spaces and calculate from them the noise in the coding variable, i.e., the spike time. Secondly, the suprathreshold filtering properties of neurons are derived, based on the phase response curves (PRCs) by perturbing the associated Fokker-Planck equations. It turns out that key characteristics of the filter, such as the DC component of the gain and the behaviour near the fundamental frequency and its harmonics are related to the particular Fourier components of the PRC and hence the bifurcation type of the neuron. With the help of the derived filter and further approximations one is able to calculate the frequency resolved signal-to-noise ration and finally the total information transmission rate of a conductance based model. Using the method of numerical continuation it is possible to calculate the change in spike time noise level as well as the filtering properties for arbitrary changes in biophysical parameter such as varying channel densities or mean input to the cell. We extend the phase reduction to include correction terms from the amplitude dynamics that are related to the curvature of the isochrons and provide a method to identify the required amplitude sensitivities numerically. It can be shown that the curvature of the isochron has a direct consequence for the noise induced frequency shift.

O ganho crescen te de desempenho nos computadores modernos tem impulsionado os trabalhos científicos nas áreas de simulação computacional. Muitos autores utilizam em suas pesquisas ferramentas comerciais que limitam seus trabalhos ao esconder os algoritmos internos destas ferramentas e dificultam a adição de dados in-vivo nestes trabalhos. Este trabalho explora esta lacuna deixada por aqueles autores. Elaboramos um arcabouço computacional capaz de reproduzir os fenômenos óticos e fisiológicos do sistema visual. Construímos com superfícies quádricas os modelos esquemáticos do olho humano e propomos um algoritmo de traçado de raio realístico. Então realizamos um estudo nos modelos esquemáticos e a partir deles mais a adição de dados in-vivo obtidos de um topógrafo de córnea extraímos informações óticas destes modelos. Calculamos os coeficientes e Zernike dos modelos para tamanhos diversos de pupila e obtivemos medidas de aberração do olho humano. Os resultados encontrados estão de acordo com os trabalhos relacionados e as simulações com dados in-vivo estão consoantes com as produzidas por um aparelho de frente de onda comerciais. Este trabalho é um esforço em aproveitar as informações adquiridas pelos equipamentos modernos de oftalmologia, além de auxiliar o entendimento de sistemas visuais biológicos acabam também em auxiliar a elaboração de sistemas de visão artificial e os projetistas de sistemas óticos / The increase in performance of the modern computers has driven scientific work in the areas of computer simulation. Many authors use in their research commercial tools that use embedding algorithms, which sources are not provided, and it makes harder and sometimes impossible, the development of novel theories or experiments. This work explores this gap left for those authors. We present a computational framework capable to reproduce the optical and physiological phenomena of the human visual system. We construct schematical models of the human eye from quadrics surfaces and consider an algorithm of realistic ray tracing. Afterward, we performed a study on schematics models and in addition we introduce, in these models, in-vivo data obtained from corneal topography machine and extract optical information. We calculate the Zernike coefficients in the models for different sizes of pupil and measures of aberration of the human eye. The results are in agreement with related work and simulations with in-vivo data are according with the produced by a commercial wave-front device. This work is an effort in using to advantage the information acquired for the modern equipment of ophthalmology, besides assisting the understanding of biological visual systems, it also helps the development of artificial vision systems and the designing of optical systems