Cette thèse invite à une analyse des rapports entre les représentations savantes et communes de l'Orient dans la littérature anglaise du XVIIIe siècle. Elle découvre un ensemble d'interactions qui constituent ces deux cultures et démontre que le rapprochement entre la mode orientale et l'orientalisme savant n'est pas antithétique. Au contraire, ces deux types de discours sur l'Orient, bien que distincts, entretiennent une relation de mimétisme qui les conduit à assumer des positions ambivalentes. Aussi, les représentations de l'Orient au XVIIIe siècle sont autre chose qu'un simple effet de mode pseudo-orientale. Elle prennent part à un projet savant qui ne s'est pas brutalement arrêté au moment de la traduction des Arabian Nights Entertainments en 1705 pour ne reprendre qu'en 1784 avec la création de la Société Asiatique de Calcutta. Cette thèse expose l'originalité d'une rencontre entre le monde de l'érudition orientaliste et le grand public, de même qu'elle dévoile l'influence réciproque du goût anglais sur les traductions des œuvres orientales et, inversement, du style oriental sur l'élaboration d'un canon poétique anglais. / This thesis analyses the relationships between the academic and the general representations of the Orient in eighteenth-century English literature. It uncovers a network of interactions which defines both cultures, and it demonstrates that the oriental vogue and knowledge of the Orient are not antithetical phenomena. Indeed, the two distinct types of discourses on the Orient function mimetically and develop ambivalent positions. Representations of the Orient in eighteenth-century English literature cannot be reduced to a pseudo-oriental craze. They are part of an enduring process of knowledge formation, which did not stop in 1705 with the translation from the French of Galland's Arabian Nights Entertainments and then suddenly reappeared in 1784 with the founding of the Asiatic Society in Calcutta. This thesis exposes a moment in time when, contrary to what had happened before, scholarship met with and actively sought a broad readership, as it also unveils the reciprocal influence of the English taste on the translations of Oriental texts and, conversely, of the oriental style on the formation of an English literary canon.

The excitement which followed the discovery of high-temperature superconductors in 1986 was short-lived, as it became clear that their current carrying capacity (the critical current density Jc) was limited by grain boundaries (GBs). In order to reduce their detrimental effects coated conductors have been developed, in which a superconducting thin film is deposited on a polycrystalline, textured substrate. Within certain temperature and magnetic field ranges, however, GBs still limit the overall Jc. This fact motivated the present thesis, for which the electrical properties of different types of coated conductors, and in particular their GBs, were investigated. Several GBs and a single grain were isolated in a tape produced by metal-organic deposition (MOD), using a novel approach based on electron backscatter diffraction and a focused ion beam microscope. Measurements of their critical current densities for fields swept in the film plane showed the expected decrease with increasing misorientation angle at low fields. At higher fields an angle dependent crossover was found, from a GB to grain limited Jc. In order to confirm this result and put it into broader perspective, the dependence of Jc on the width of polycrystalline tracks was studied, and then explained in terms of the behaviour of the single GBs. Investigations using low-temperature scanning laser microscopy rounded out the picture, which also showed GB dissipation at certain angles and grain limitation at others. In measurements on samples produced by metal-organic chemical vapour deposition (MOCVD) characteristic differences compared to the MOD film were found. While both conductors exhibited high values of Jc, the variation with in-plane angle was significantly stronger for the MOCVD conductor, which can be explained by its sharper texture. In a track patterned perpendicular to the tape direction the phenomenon of vicinal channelling was observed, which previously was known only from films on single crystal substrates. Finally, an isolated boundary showed very high values of Jc, consistent with its low misorientation. In order to better understand how the substrate influences the superconducting properties, measurements were carried out on otherwise identical samples grown on different substrates. A tape with grains elongated along its rolling direction showed particularly good properties at all examined field orientations. This extends the previously reported result that high aspect ratios are beneficial at fields applied perpendicular to the tape plane.

The cyber-physical systems (CPS), such as smart grid and intelligent transportation system, permeate into our modern societies recently. The infrastructures in such systems are closely interconnected and related, e.g., the intelligent transportation system is based on the reliable communication system, which requires the stable electricity provided by power grid for the proper function. We call such mutually related systems interdependent networks. This thesis addresses the cascading failure issue in interdependent cyber physical system. We consider CPS as a system that consists of physical-resource and computational-resource networks. The failure in physical-resource network might cause the failures in computational-resource network, and vice versa. This failure may recursively occur and cause a sequence of failures in both networks. In this thesis, we propose two novel interdependence models that better capture the interdependent networks. Then, we study the effect of cascading failures using percolation theory and present the detailed mathematical analysis on failure propagation in the system. By calculating the size of functioning parts in both networks, we analyze the robustness of our models against the random attacks and failures. The cascading failures in smart grid is also investigated, where two types of cascading failures are mixed. We estimate how the node tolerance parameter T (ratio of capacity to initial workload) affect the system performance. This thesis also explores the small clusters. We give insightful views on small cluster in interdependent networks, under different interdependence models and network topologies.

Algumas metapopulações de espécies, como formigas, vivem em colônias que crescem durante algum tempo e depois colapsam. Após o colapso poucos indivíduos sobrevivem. Esses indivíduos se dispersam tentando fazer novas colônias que podem ou não se estabelecer dependendo do ambiente que encontram. Recentemente, Schinazi (2015) usou cadeias de nascimento e morte em ambientes aleatórios para modelar tais populações, e mostrou que a dispersão aleatória é uma boa estratégia para a sobrevivência da população. Nesta tese, introduzimos outros modelos estocásticos de colonização e colapso para os quais consideramos restrições espaciais e diferentes tipos de colapsos. Obtemos para esses novos modelos condições de sobrevivência e extinção. Debatemos algumas situações nas quais a dispersão nem sempre é uma boa estratégia de sobrevivência. Além disso, discutimos a relação destes modelos com outros conhecidos na literatura. Técnicas de percolação, acoplamento e comparação com processos de ramificação convenientemente definidos são usadas para obter os resultados aqui estabelecidos. / Some metapopulations, such as ants, live in colonies that grow for a while and then collapse. Upon collapse, very few individuals survive. These individuals disperse, trying to establish new colonies that may or may not settle, depending on the environment they encounter. Recently, Schinazi (2015) used birth and death chains in random environments to model such populations, and showed that random dispersion is a good strategy for the survival of the population. In this thesis, we introduce other stochastic models of colonization and collapse for which we consider spatial constraints and different kinds of collapse. We obtain conditions for survival and extinction in these new models. We discuss some situations in which dispersion is not always a good survival strategy. In addition, we discuss the relation of these models to others known in the literature. Percolation and coupling techniques and comparison with suitably defined branching processes are used to obtain the results set forth herein.

The foreseen massive deployment of the internet of things (IoT) is expected to suffer from high security risks. This mainly results from the difficulty to monitor and cure the IoT devices in such large-scale deployment. In this thesis, we propose a spatial random deployment of special nodes (firewalls) which can detect and cure infected nodes within certain radius. An important concern is to add sufficient number of firewalls to make an epidemics finite and, hence, prevent malware outbreak over the whole network. The problem will be analyzed using percolation theory. Namely, we derive an upperbound for the critical intensity of spatial firewalls which guarantees prevention of large-scale network epidemics, regardless of the intensity of regular nodes. Using tools from percolation theory, we analyze the proposed solution and show the conditions required to ensure its efficiency.

No description available.

No description available.

Comets, remnants of the solar system's formation, exhibits partially unexplained outbursts that are closely tied to the physical structure of the nucleus. To investigate outbursts, we employed pore network modeling techniques, such as the Bower-Watson algorithm and Voronoi diagrams, to better represent the nucleus' complex porous structure and simulate gas transfer processes. We examined heat diffusion in the comet's subsurface and its influence on crystallization. The extra heat generated by crystallization can shift the crystalline front deeper into the nucleus, accelerating subsurface evaporation rates. This process results in the formation of a thicker ice mantle with reduced porosity on the surface, trapping evaporated gas in the underlying layers. As gas pressure accumulates over time, the mantle eventually succumbs to the buildup. By applying percolation theory, we identified the critical point at which trapped gas breaks through the surface, ultimately leading to a better understanding of comet outburst formation.

Consider infecting a subset $A_0 \subseteq V(G)$ of the vertices of a graph $G$. Let an uninfected vertex $v \in V(G)$ become infected if $|N_G(v) \cap A_0| \geq r$, for some integer $r$. Define $A_t = A_{t-1} \cup \{v \in V(G) : |N_G(v) \cap A_{t-1}| \geq r \},$ and say that the set $A_0$ is \emph{lethal} under $r$-neighbor percolation if there exists a $t$ such that $A_t = V(G)$. For a graph $G$, let $m(G,r)$ be the size of the smallest lethal set in $G$ under $r$-neighbor percolation. The problem of determining $m(G,r)$ has been extensively studied for grids $G$ of various dimensions. We define $$m(a_1, \dots, a_d, r) = m\left (\prod_{i=1}^d [a_i], r\right )$$ for ease of notation. Famously, a lower bound of $m(a_1, \dots, a_d, d) \geq \frac{\sum_{j=1}^d \prod_{i \neq j} a_i}{d}$ is given by a beautiful argument regarding the high-dimensional ``surface area" of $G = [a_1] \times \dots \times [a_d]$. While exact values of $m(G,r)$ are known in some specific cases, general results are difficult to come by. In this thesis, we introduce a novel technique for viewing $3$-neighbor lethal sets on three-dimensional grids in terms of lethal sets in two dimensions. We also provide a strategy for recursively building up large lethal sets from existing small constructions. Using these techniques, we determine the exact size of all lethal sets under 3-neighbor percolation in three-dimensional grids $[a_1] \times [a_2] \times [a_3]$, for $a_1,a_2,a_3 \geq 11$. The problem of determining $m(n,n,3)$ is discussed by Benevides, Bermond, Lesfari and Nisse in \cite{benevides:2021}. The authors determine the exact value of $m(n,n,3)$ for even $n$, and show that, for odd $n$, $$\ceil*{\frac{n^2+2n}{3}} \leq m(n,n,3) \leq \ceil*{\frac{n^2+2n}{3}} + 1.$$ We prove that $m(n,n,3) = \ceil*{\frac{n^2+2n}{3}}$ if and only if $n = 2^k-1$, for some $k >0$. Finally, we provide a construction to prove that for $a_1,a_2,a_3 \geq 12$, bounds on the minimum lethal set on the the torus $G = C_{a_1} \square C_{a_2} \square C_{a_3}$ are given by $$2 \le m(G,3) - \frac{a_1a_2 + a_2a_3 + a_3a_1 -2(a_1+a_2+a_3)}{3} \le 3.$$ / Graduate

A Monte Carlo model is developed for predicting electrical conductivity of carbon nanofiber composite materials. The conductive nanofibers are models as both 2D and 3D network of finite sites that are randomly distributed. The percolation behavior of the network is studied using the Monte Carlo method, which leads to the determination of the percolation threshold. The effect of the nanofiber aspect ratio on the critical nanofiber volume rate is investigated in the current model, each of the nanofibers needs five independent geometrical parameters (i.e., three coordinates in space and two orientation angles) for its identification. There are three controlling parameters for each nanofiber, which includes the nanofiber length, the nanofiber diameter, and the nanofiber aspect ratio. The simulation results reveal a relationship between the fiber aspect ratio and the percolation threshold: the higher the aspect ratio, the lower the threshold. With the simulation results obtained from the Monte Carlo model, the effective electrical conductivity of the composite is then determined by assuming the conductivity is proportional to the ratio of the number of nanofibers forming the largest cluster to the total number of nanofibers. The numerical results indicate that as the volume rate reaches a critical value, the conductivity starts to rise sharply. These obtained simulation results agree fairly with experimental and numerical data published earlier by others. In addition, we investigate the convergence of the current percolation model. We also find the tunneling effect does not affect the critical volume rate greatly. We propose that the percolation model is not scalable as well.