Dissertations / Theses on the topic 'Scale-free'
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Ang, Wee Horng. "Scale-free information systems networks." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34554.
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Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, 2006.Includes bibliographical references (leaves 77-79).
Many real, complex networks have been shown to be scale-free. Scale-free in networks mean that their degree distribution is independent of the network size, have short path lengths and are highly clustered. We identify the qualities of scale-free networks, and discuss the mathematical derivations and numerically simulated outcomes of various deterministic scale-free models. Information Systems networks are a set of individual Information Systems that exchange meaningful data among themselves. However, for various reasons, they do not naturally grow in a scale-free manner. In this topic, we will specifically examine a technique proposed by MITRE that allows information to be exchanged in an efficient manner between Information System nodes. With this technique, we will show that a scale-free Information System Network is sound in theory and practice, state the characteristics of such networks and demonstrate how such a system can be constructed.
by Wee Hong Ang.
S.M.
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Xulvi-Brunet, Ramon. "Structural properties of scale-free networks." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=984083197.
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Brockmann, Dirk. "Superdiffusion in scale-free inhomogeneous environments." Doctoral thesis, [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969638884.
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Xulvi-Brunet, Ramon. "Structural properties of scale-free networks." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15608.
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Netzwerke sind überall, von der elektrischen Stromversorgung über die Biochemie der Zellen, das Internet bis hin zu sozialen Netzen. Netzwerke als mathematisches Konzept haben sich in den letzten Jahren zu einem wichtigen Werkzeug der Beschreibung komplexer Systeme entwickelt. Ihre grundlegende Eigenschaft ist, dass sie aus einer grö{ss}en Anzahl dynamischer Elemente bestehen, die sich gegenseitig beeinflussen und dabei nicht linear gekoppelt sind. Die moderne Netzwerkwissenschaft will die Wechselwirkung zwischen den einzelnen Untereinheiten erklären und davon ausgehend verständlich machen, auf welche Weise Prozesse auf einem Netzwerk stattfinden können. Zum Beispiel wird untersucht, wie die Struktur sozialer Netze die Ausbreitung von Information oder von Krankheiten beeinflusst, wie die Topologie des World Wide Web das Surf-Verhalten oder die Funktionalität von Suchmaschinen beeinträchtigt oder welche Auswirkungen die Hierarchie in ökologischen Nischen auf die Populationsdynamik der einzelnen Spezies hat. Darüber hinaus gilt es herauszufinden, welche grundlegenden Prinzipien der Evolution realer Netzwerke zugrunde liegen, das heißt nach welchen Regeln sich einerseits die Untereinheiten entwickeln und welchen Einfluss andererseits deren Vernetzung hat. Die vorliegende Dissertation beschäftigt sich sowohl mit der Topologie verschiedener Netzwerke als auch mit den der Evolution zugrunde liegenden Prinzipien. Schwerpunkte liegen dabei auf den folgenden zwei Aspekten: erstens dem Einfluss von so gennanten ``vertex-pair correlations'''', das heißt Korrelationen zwischen den Untereinheiten, auf die Topologie und zweitens der Auswirkung der Geographie auf die Netzwerkentwicklung. Es wird der bedeutende Einfluss aufgezeigt, den die Korrelationen auf wichtige statistische Größen der Netzwerke haben. Weiterhin analysieren wir die Perkolationseigenschaften, die Aufschluss über die Empfindlichkeit gegenüber Störungen in der Vernetzung geben. Damit können zum Beispiel Fragen aus der Epidemiologie diskutiert werden. Es zeigt sich, dass die Topologie vieler Netzwerke und ihre Perkolationseigenschaften deutlich von Korrelationen beeinflusst werden. Schließlich untersuchen wir im letzten Teil dieser Arbeit, wie die Einbettung von Netzwerken in eine endlich-dimensionale Geographie auf die Modellierung und Entwicklung Web-ähnlicher Systeme Einfluss nimmt.Networks are all around us, from electrical power grids to the biochemistry of cells, from the Internet to social webs. The mathematical concept of network has recently been turned into an important tool for describing complex systems, whose principal characteristic is that they consist of a large number of mutually interacting dynamical parts which are coupled in a nonlinear fashion. Modern network science attempts to explain the structure of interactions between the subunits of a system in order to understand their functioning and the processes taking place in them. It tries, for instance, to grasp how the structure of social networks affects the spread of information or human diseases, how the structure of the World Wide Web influences the search engines and surfing behavior, or how the hierarchy of ecological niches affects population dynamics. Beyond this, the ultimate goal of network science is to discover what generating principles exist behind the evolution of real systems. It tries to find the fundamental principles under which the subunits evolve, and the wiring of interactions. This thesis centres both on the study of the topological structure of networks and the analysis of the underlying principles responsible for their evolution. More specifically, it concentrates on the following aspects: the influence of vertex-pair correlations on network topology, the network percolation problem, which is closely related to the spreading of epidemics and the robustness of networks, and the effects of geography as a generating element. We show that important topological and percolation properties change considerably when modifying the connection probabilities between vertices, and that geography as well plays a crucial role in the modeling of evolving real web-like systems.
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Martin, Nicolas. "Network partitioning algorithms with scale-free objective." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALT001.
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En raison de la complexité inhérente à l’analyse de réseau de très grande taille, l’élaboration d’algorithmes de partitionnement et diverses problématiques connexes sont traitées au long de cette thèse. Dans un premier temps, une question préliminaire est traitée: puisque les nœuds au sein d’une partie ne sont pas nécessairement connexes, comment quantifier l’impact d’une contrainte de connexité ? Nous proposons ensuite un algorithme de partitionnement assurant que le réseau réduit soit scale-free. Ceci permet de tirer profit des propriétés intrinsèques de ce type de réseaux. Nous nous intéressons également aux propriétés à préserver pour respecter la nature physique et dynamique du réseau initial. Dans une troisième partie, nous proposons une méthode pour identifier les nœuds à mesurer dans un réseau pour garantir une reconstruction efficace de la valeur moyenne des autre nœuds. Finalement, nous proposons trois applications: la première concerne le trafic routier et nous montrons que notre premier algorithme de partitionnement permet d’obtenir un réseau réduit émulant efficacement le réseau initial. Les deux autres applications concernent les réseaux d’épidémiologie. Dans la première nous montrons qu’un réseau réduit scale-free permet de construire une stratégie efficace d’attribution de soin au sein d’une population. Dans la dernière application, nous tirons profit des résultats sur la reconstruction de moyenne pour estimer l’évolution d’une épidémie dans un réseau de grande tailleIn light of the complexity induced by large-scale networks, the design of network partitioning algorithms and related problematics are at the heart of this thesis. First, we raise a preliminary question on the structure of the partition itself: as the parts may includes disconnected nodes, we want to quantify the drawbacks to impose the nodes inside each part to be connected. Then we study the design of a partitioning algorithm inducing a reduced scale-free network. This allows to take advantage of the inherent features of this type of network. We also focus on the properties to preserve to respect the physical and dynamical profile of the initial network. We investigate then how to partition a network between measured and unmeasured nodes ensuring that the average of the unmeasured nodes can be efficiently reconstructed. In particular we show that, under hypothesis, this problem can be reduced to a problem of detection of subgraph with particular properties. Methods to achieve this detection are proposed. Finally, three applications are presented: first we apply the partitioning algorithm inducing scale-freeness to a large-scale urban traffic network. We show then that, thanks to the properties preserved through the partition, the reduced network can be used as an abstraction of the initial network. The second and third applications deal with network epidemics. First, we show that the scale-freeness of the abstracting network can be used to build a cure-assignation strategy. In the last application, we take advantage of the result on average reconstruction to estimate the evolution of a disease on a large-scale network
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Rodrigues, Pedro Miguel Fonseca. "Scale-free networks and scalable interdomain routing." Master's thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/4336.
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Trabalho apresentado no âmbito do Mestrado em Engenharia Informática, como requisito parcial para obtenção do grau de Mestre em Engenharia InformáticaThe exponential growth of the Internet, due to its tremendous success, has brought to light some limitations of the current design at the routing and arquitectural level, such as scalability and convergence as well as the lack of support for traffic engineering, mobility, route differentiation and security. Some of these issues arise from the design of the current architecture, while others are caused by the interdomain routing scheme - BGP. Since it would be quite difficult to add support for the aforementioned issues, both in the interdomain architecture and in the in the routing scheme, various researchers believe that a solution can only achieved via a new architecture and (possibly) a new routing scheme. A new routing strategy has emerged from the studies regarding large-scale networks, which is suitable for a special type of large-scale networks which characteristics are independent of network size: scale-free networks. Using the greedy routing strategy a node routes a message to a given destination using only the information regarding the destination and its neighbours, choosing the one which is closest to the destination. This routing strategy ensures the following remarkable properties: routing state in the order of the number of neighbours; no requirements on nodes to exchange messages in order to perform routing; chosen paths are the shortest ones. This dissertation aims at: studying the aforementioned problems, studying the Internet configuration as a scale-free network, and defining a preliminary path onto the definition of a greedy routing scheme for interdomain routing.
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Kent, Stuart Thomas. "Multi-Scale Conformal Maps and Free Boundary Problems." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301534.
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In this dissertation, we study free boundary problems that describe equilibrium configurations of electromechanical systems consisting of a conducting elastic sheet deflected by an external charge distribution. Such systems are non-local in nature - the electrostatic pressure experienced by any individual point on the sheet depends on the entire deflection profile (as a result of the requirement that the deflected sheet must remain an equipotential). The magnitude of the electrostatic pressure varies quadratically with the magnitude of the local electric field. Similar non-local free boundary problems arise in two-layer fluid systems forced by withdrawal flows, but the normal viscous stress experienced by the fluid-fluid interface instead varies linearly with the local velocity gradients. The analysis presented focuses on two configurations in particular: the electromechanical system described above, forced by a point charge, and an artificially modified version of the same electromechanical system in which the induced electrostatic pressure varies linearly with the local electric field and the forcing is provided by an electric dipole. This second model is constructed as a crude approximation of the two-layer fluid flow forced by a point sink, and is primarily used to explore the influence of the forcing exponent on the bifurcation structure and solution types of the associated system. Our main contribution is the development of new techniques for the analysis and efficient numerical computation of large-deflection profiles for the true electromechanical system. The induced charge on such profiles accumulates near the interface tip, so that the geometry there is primarily determined by a balance between elastic and electrostatic forces. Away from the tip, the electrostatic pressure is low and the interface relaxes under the influences of gravity and elasticity only. Such interfaces exhibit features on widely disparate length scales. We exploit this separation of the interface into two regions dominated by different force balances to create a separate representation of each region (in appropriately rescaled coordinates), and then match the two representations together while ensuring that the relationship between local induced stress and global interface geometry is respected. This is achieved by combining tools and results from complex analysis and the method of matched asymptotic expansions.
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Guadamuz, Andres. "Networks, complexity and internet regulation scale-free law." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7795.
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This book, then, starts with a general statement: that regulators should try, wherever possible, to use the physical methodological tools presently available in order to draft better legislation. While such an assertion may be applied to the law in general, this work will concentrate on the much narrower area of Internet regulation and the science of complex networks The Internet is the subject of this book not only because it is my main area of research, but also because –without over-emphasising the importance of the Internet to everyday life– one cannot deny that the growth and popularisation of the global communications network has had a tremendous impact on the way in which we interact with one another. The Internet is, however, just one of many interactive networks. One way of looking at the complex and chaotic nature of society is to see it as a collection of different nodes of interaction. Humans are constantly surrounded by networks: the social network, the financial network, the transport network, the telecommunications network and even the network of our own bodies. Understanding how these systems operate and interact with one another has been the realm of physicists, economists, biologists and mathematicians. Until recently, the study of networks has been mainly theoretical and academic, because it is difficult to gather data about large and complex systems that is sufficiently reliable to support proper empirical application. In recent years, though, the Internet has given researchers the opportunity to study and test the mathematical descriptions of these vast complex systems. The growth rate and structure of cyberspace has allowed researchers to map and test several previously unproven theories about how links and hubs within networks interact with one another. The Web now provides the means with which to test the organisational structures, architecture and growth of networks, and even permits some limited prediction about their behaviour, strengths and vulnerabilities. The main objective of this book is first and foremost to serve as an introduction to the wider legal audience to some of the theories of complexity and networks. The second objective is more ambitious. By looking at the application of complexity theory and network science in various areas of Internet regulation, it is hoped that there will be enough evidence to postulate a theory of Internet regulation based on network science. To achieve these two goals, Chapter 2 will look in detail at the science of complex networks to set the stage for the legal and regulatory arguments to follow. With the increase in reliability of the descriptive (and sometimes predictive) nature of network science, a logical next step for legal scholars is to look at the legal implications of the characteristics of networks. Chapter 3 highlights the efforts of academics and practitioners who have started to find potential uses for network science tools. Chapter 4 takes this idea further, and explores how network theory can shape Internet regulation. The following chapters will analyse the potential for application of the tools described in the previous chapters, applying complexity theory to specific areas of study related to Internet Law. Chapter 5 deals with the subject of copyright in the digital world. Chapter 6 explores the issue of peer-production and user-generated content using network science as an analytical framework. Chapter 7 finishes the evidence section of the work by studying the impact of network architecture in the field of cybercrime, and asks whether the existing architecture hinders or assists efforts to tackle those problems. It is clear that these are very disparate areas of study. It is not the intention of this book to be overreaching in its scope, although I am mindful that it covers a lot of ground and attempts to study and describe some disciplines that fall outside of my intellectual comfort zone. While the focus of the work is the Internet, its applications may extend beyond mere electronic bits. Without trying to be over-ambitious, it is my strong belief that legal scholarship has been neglectful in that it has been slow to respond to the wealth of research into complexity. That is not to say that there has been no legal research on the topic, but it would seem that lawyers, legislators and policy-makers are reluctant to consider technical solutions to legal problems. It is hoped then that this work will serve as a stepping stone that will lead to new interest in some of the theories that I describe.
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Weinstein, Lee. "Scale free networks and their power law distribution." Diss., Connect to the thesis, 2005. http://hdl.handle.net/10066/3880.
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Hollingshad, Nicholas W. "A Non-equilibrium Approach to Scale Free Networks." Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc149609/.
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Many processes and systems in nature and society can be characterized as large numbers of discrete elements that are (usually non-uniformly) interrelated. These networks were long thought to be random, but in the late 1990s, Barabási and Albert found that an underlying structure did in fact exist in many natural and technological networks that are now referred to as scale free. Since then, researchers have gained a much deeper understanding of this particular form of complexity, largely by combining graph theory, statistical physics, and advances in computing technology. This dissertation focuses on out-of-equilibrium dynamic processes as they unfold on these complex networks. Diffusion in networks of non-interacting nodes is shown to be temporally complex, while equilibrium is represented by a stable state with Poissonian fluctuations. Scale free networks achieve equilibrium very quickly compared to regular networks, and the most efficient are those with the lowest inverse power law exponent. Temporally complex diffusion also occurs in networks with interacting nodes under a cooperative decision-making model. At a critical value of the cooperation parameter, the most efficient scale free network achieves consensus almost as quickly as the equivalent all-to-all network. This finding suggests that the ubiquity of scale free networks in nature is due to Zipf's principle of least effort. It also suggests that an efficient scale free network structure may be optimal for real networks that require high connectivity but are hampered by high link costs.
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Iyer, Bharat Vishwanathan. "Capacity and scale-free dynamics of evolving wireless networks." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/1359.
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Many large-scale random graphs (e.g., the Internet) exhibit complex topology, nonhomogeneous spatial node distribution, and preferential attachment of new nodes. Current topology models for ad-hoc networks mostly consider a uniform spatial distribution of nodes and do not capture the dynamics of evolving, real-world graphs, in which nodes "gravitate" toward popular locations and self-organize into non-uniform clusters. In this thesis, we first investigate two constraints on scalability of ad-hoc networks network reliability and node capacity. Unlike other studies, we analyze network resilience to node and link failure with an emphasis on the growth (i.e., evolution) dynamics of the entire system. Along the way, we also study important graph-theoretic properties of ad-hoc networks (including the clustering coefficient and the expected path length) and strengthen our generic understanding of these systems. Finally, recognizing that under existing uniform models future ad-hoc networks cannot scale beyond trivial sizes, we argue that ad-hoc networks should be modeled from an evolution standpoint, which takes into account the well-known "clustering" phenomena observed in all real-world graphs. This model is likely to describe how future ad-hoc networks will self-organize since it is well documented that information content distribution among end-users (as well as among spatial locations) is non-uniform (often heavy-tailed). Results show that node capacity in the proposed evolution model scales to larger network sizes than in traditional approaches, which suggest that non-uniformly clustered, self-organizing, very large-scale ad-hoc networks may become feasible in the future.
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Benhaiem, David. "Non linear gravitational clustering in scale free cosmological models." Paris 6, 2013. http://www.theses.fr/2013PA066653.
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The formation of structures in the universe is one of the major questions in cosmology, and numerical N body simulations are the primary instrument used to probe the non linear clustering. However, analytical understanding of this regime remains limited. To explore this regime we study a family of Einstein de Sitter models with cold power law initial conditions. In practice, this means that we have two control parameters on which we can study the dependance of simple crucial analytical predictions for these models : self similarity of the clustering, and the correlation exponents when this clustering is stable. We study first an analogous one dimensional class of models, and find that the stable clustering predictions provide an excellent approximation in the non linear regime for most of the parameter space, while a region in which clustering appears to be universal is observed close to the static limit. We then study N body simulations of the three dimensional models. We find, in the part of the parameter space we can constrain well numerically, that the exponents of the self-similar two point correlation function in the strongly non-linear regime are in excellent agreement with those predicted by stable clustering. Furthermore, preliminary results on the halos extracted from our simulations indicate that the mass profiles of these non-linear structures are well described, as a power law with exponents clearly dependent on the initial conditions and the cosmology, and specifically, correlated with the stable clustering exponentsLa formation des structures dans l’univers est l’une des questions majeures en cosmologie et le régime non linéaire est principalement étudié à l’aide de simulations numériques à N corps. Cependant, la compréhension de ce régime reste limitée. Afin de l’explorer nous étudions une famille de modèles cosmologiques Einstein de Sitter avec des conditions initiales froides en loi de puissance. En pratique, cela signifie que nous avons deux paramètres de contrôle sur lesquels nous pouvons étudier la dépendance de prédictions analytiques simples pour ces modèles: l’auto similarité de l’agrégation gravitationnelle et les exposants dans les corrélations lorsque cette agrégation est stable. Nous commençons par étudier une classe analogue de modèles à une dimension et nous trouvons que l’agrégation gravitationnelle stabilisée est une excellente approximation dans le régime non linéaire pour une grande partie de l’espace des paramètres, alors qu’une région, dans laquelle l’agrégation apparait universel, est observée proche de la limite statique. Nous étudions ensuite des simulations cosmologiques à N corps dans le cas de modèles à trois dimensions. Nous trouvons, pour la partie de l’espace des paramètres que nous pouvons contraindre, que les exposants mesurés dans les fonctions de correlation auto-similaire sont en excellent accord avec ceux prédit par l’hypothèse de l’agrégation stabilisée. De plus, nos résultats préliminaires sur les halos extraits de nos simulations indiquent que les profiles de densité de ces structures non linéaires peuvent être décrits par une loi de puissance avec des exposants dépendant clairement des conditions initiales et les paramètres cosmologiques, et plus spécifiquement, corrélés avec les exposants prédit par l’agrégation stabilisée
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Farris, Andrew. "Drop Impact Reliability Testing Lead-Free Chip Scale Packages." DigitalCommons@CalPoly, 2008. https://digitalcommons.calpoly.edu/theses/21.
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Mobile and handheld electronics devices such as digital cameras, cell phones, and personal digital assistants (PDAs) are prone to be dropped in their lifetime. The drop event may result in failure of solder joints inside these devices. The importance and widespread use of these devices in both business and leisure activities continues to increase, so device failure is increasingly costly and inconvenient. Recently the European Union (EU) Restriction of Hazardous Substances (RoHS) and other countries' lead-free directives banned the use of lead in consumer electronics products. While this is a responsible environmental change for the electronics industry, it requires the introduction of new solders and soldering processes, and signals a major change in production methods as lead-based solders are no longer used in these devices. Thus, it is critical to study the drop impact reliability of lead-free solder joints. This thesis discusses the reliability of Chip Scale Packages (CSPs) in drop impact, with and without the CSPs being edge-bonded, using two failure detection systems and presents the component failure sequence as observed by each system. To enable this study a high-speed data acquisition system, capable of in-situ detection of transitional solder interconnect failure, was developed at Cal Poly for drop impact reliability testing. Edge-bonding is shown to significantly improve drop impact reliability of CSPs.
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Pelude, Linda. "Networks among injection drug users: Random or scale-free?" Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27903.
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The primary goal of this research was to identify whether the structure of the network of individuals who inject drugs and share drug injection equipment in Winnipeg, Canada may be scale-free. Recently, sexual networks have been found to be scale-free in a wide range of populations which has important implications in terms of the spread of disease. Epidemic thresholds do not exist in a scale-free network and as a result even weakly infectious viruses can spread easily through a network of contacts. By analogy, identifying the structure of contacts formed by individuals in other infectious disease networks may also help to define transmission dynamics which can be used to develop more effective interventions.
In a series of three papers the scientific literature from a variety of disciplines including physics, epidemiology, mathematical, biological and computer sciences relating to scale free networks is reviewed and integrated; methods used to identify scale-free networks are tested and compared among individuals who inject drugs in Winnipeg, Canada using data from two network studies (a pilot study and a main study); and potential new interventions that could be implemented to help reduce the transmission of HIV and HCV among individuals who inject drugs by the existing needle exchange program are recommended based on the results.
Keywords: Scale-free networks, injection drug use, epidemiology, network analysis
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Spencer, Jason Joseph Lawrence. "An investigation into the scale-free nature of heterogeneous networks." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/17268/.
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In order to support a wide variety of services, to different user types, and under a variety of geographic situations, telecommunications networks are typically composed of a variety of layers and heterogeneous technologies. Layers (in terms of the OSI 7 layer model) such as the transmission layer (e.g. WDM), the data link layer (also known as the transport network e.g. SDH, Ethernet) and the network layer (e.g. IP). These layers may also contain logical layers within them such as virtual paths, as well as overlay networks such as a peer-to-peer system. No single layer is independent of the adjacent layer and the provisioning requirements of one layer become the demand on the layer below. Similarly the available resources become the delivered quality of service to the layer above. This thesis is concerned with the design aspects of various layers and how they affect each other’s topology. The thesis’ main focus is topological analysis and modelling of layers, and its presents a detailed analysis of a deployed national SDH network, examining bandwidth distribution, topology, geography and the demand pattern. The thesis finds that even the strictly planned and provisioned SDH network, whose architecture contain explicit structures and hierarchy, has notable power-law traits in various metrics of the topology; traits similar to those which have been shown to exist in the Internet, as well as non-technological networks such as social graphs. There is also and examination of the protocols and architectures of the IP and SDH standards for features that affect topological development. With a better understanding of the layers, design goals and assumptions are deduced and implemented in a new topology simulator called MITIE. MITIE (Modular Inter-layer feedback Topology InvEstigation tool and simulator) is a tool designed to investigate inter-layer feedback and differs from existing topology generator in that it considers the effect of serviced demands and allows the capacity usage to affect the further development of the topology. The thesis presents results from a series of experiments with MITIE and demonstrates that as the network is re-designed to accommodate demand, it can tend to power-law compliant topologies under the correct circumstances. Such a reactive topology model could also be used to investigate the effect of topological change and the effect of increasing the number of layers (such as adding MPLS), or the use of peer-to-peer overlay networks, or the decrease of the number of layers (IP over WDM). The model could also be used to investigate link and node failure/addition and the real effect which will propagate through the rest of the multi-layer network.
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Dreilinger, Daniel Ethan 1970. "Scale free information retrieval : visually searching and navigating the web." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/61097.
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Ruffels, Aaron. "Model-Free Damage Detection for a Small-Scale Steel Bridge." Thesis, KTH, Bro- och stålbyggnad, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232363.
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Around the world bridges are ageing. In Europe approximately two thirds of all railway bridges are over 50 years old. As these structures age, it becomes increasingly important that they are properly maintained. If damage remains undetected this can lead to premature replacement which can have major financial and environmental costs. It is also imperative that bridges are kept safe for the people using them. Thus, it is necessary for damage to be detected as early as possible. This research investigates an unsupervised, model-free damage detection method which could be implemented for continuous structural health monitoring. The method was based on past research by Gonzalez and Karoumi (2015), Neves et al. (2017) and Chalouhi et al. (2017). An artificial neural network (ANN) was trained on accelerations from the healthy structural state. Damage sensitive features were defined as the root mean squared errors between the measured data and the ANN predictions. A baseline healthy state could then be established by presenting the trained ANN with more healthy data. Thereafter, new data could be compared with this reference state. Outliers from the reference data were taken as an indication of damage. Two outlier detection methods were used: Mahalanobis distance and the Kolmogorov-Smirnov test. A model steel bridge with a span of 5 m, width of 1 m and height of approximately 1.7 m was used to study the damage detection method. The use of an experimental model allowed damaged to be freely introduced to the structure. The structure was excited with a 12.7 kg rolling mass at a speed of approximately 2.1 m/s (corresponding to a 20.4 ton axle load moving at 47.8 km/h in full scale). Seven accelerometers were placed on the structure and their locations were determined using an optimal sensor placement algorithm. The objectives of the research were to: identify a number of single damage cases, distinguish between gradual damage cases and identify the location of damage. The proposed method showed promising results and most damage cases were detected by the algorithm. Sensor density and the method of excitation were found to impact the detection of damage. By training the ANN to predict correlations between accelerometers the sensor closest to the damage could be detected, thus successfully localising the damage. Finally, a gradual damage case was investigated. There was a general increase in the damage index for greater damage however, this did not progress smoothly and one case of ‘greater’ damage showed a decrease in the damage index.
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Farris, Andrew Liddicoat Albert A. "Drop impact reliability testing lead-free chip scale packages : a thesis /." [San Luis Obispo, Calif. : California Polytechnic State University], 2008. http://digitalcommons.calpoly.edu/theses/21/.
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Thesis (M.S.)--California Polytechnic State University, 2008.Major professor: Albert Liddicoat, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Electrical Engineering." "June 2008." Includes bibliographical references (leaves 70-73). Also available online. Also available on microfiche (2 sheets).
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Caurio, Maurizio. "Simulazione della creazione e della stabilità di una scale-free network." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/1838/.
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Stevens, M. L. (Michael Louis). "A scale-free analysis of magnetic holes in the solar wind." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39568.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.Includes bibliographical references (p. 45-47).
Magnetic holes are isolated intervals of depleted interplanetary magnetic field (IMF) strength on timescales of several seconds to several hours. These intervals have been seen as often as several times per day in the ecliptic and at high heliospheric latitudes from 1 AU to 5.4 AU. We present a scale-free statistical technique for identifying magnetic holes and evaluating their significance relative to turbulent fluctuations in the solar wind. We apply this technique in a comprehensive search for magnetic holes in the Wind and ACE magnetometer data streams through 2004. Using magnetic field and ion measurements on the Wind spacecraft, we present the first statistical study of magnetic hole plasma signatures on the kinetic scale and we present a comparison of magnetic holes as kinetic and microscale phenomena. Magnetic holes are shown to be pressure-balanced structures with similar properties on all scales. Temperature anisotropy measurements are combined with magnetic field measurements to give direct evidence that the mirror-mode instability in the solar wind is a likely source of magnetic holes. Two-satellite correlations between ACE and Wind indicate that magnetic holes are stationary with respect to the solar wind and elongated along the IMF.
by M.L. Stevens.
S.M.
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Tor, Ali Hakan. "Derivative Free Algorithms For Large Scale Non-smooth Optimization And Their Applications." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615700/index.pdf.
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Kumari, Durgesh R. "Ad-hoc limited scale-free models for unstructured peer-to-peer networks." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1472962.
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Liu, Yueli Johnson R. Wayne. "Lead-free assembly and reliability of chip scale packages and 01005 components." Auburn, Ala., 2006. http://hdl.handle.net/10415/1311.
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Hurley, Daniel J. "Model of neocortical connectivity based on the architecture of scale-free networks." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013364.
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Coutinho, Bruno Gabriel Coelho. "Kuramoto model aplicado a um star graph e a redes scale-free." Master's thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/9669.
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Mestrado em FísicaO trabalho realizado teve como objetivo tentar compreender o efeito de hubs no Kuramoto model, para tal foram analisados dois sistemas diferentes. No primeiro, o Kuramoto model foi aplicado a um hub isolado, revelando-se que, para as distribuições analisadas, a frequência natural do oscilador central desempenha um papel decisivo no comportamento do sistema. Se a diferença entre esta frequência e o valor médio das frequências naturais dos vizinhos do oscilador central for menor que um certo valor, não existe transição de fase no sistema. No entanto, se a diferença for acima desse mesmo valor, o sistema passa a exibir uma transição de fase de primeira ordem. No segundo modelo, foi introduzida uma correlação linear entre a frequência natural do nodo e o seudegree e aplicado a redes Erdr˝os-Rénly e scale-free. Desta forma, foi possível criar uma rede em no caso de existirem hubs, estes apresentam frequências naturais distintas das dos seus vizinhos. Para estudar analiticamente o sistema foi usado annealed network approximation e posteriormente comparado com simulações. Os resultados apontam para a existência de uma transição de fase de segunda ordem para redes Erdr˝os-Rénly e scale-free com > 3 e a existência de uma transição de fase de primeira ordem para redes scale-free com 2 < < 3.
The aim of this work is to get some insight on the effect of hubs in Kuramoto model. In order to achieve our goal, we analyze two different systems. In the first system, we study the behavior of an isolated hub using analytic calculus and comparing with simulations. For the analyzed distributions, we find that the central oscillator plays a decisive role in the general behavior of the system. There is no phase transition in the system if the difference between the central oscillator natural frequency and the mean value of his neighbor’s natural frequencies is smaller than a certain value. In contrast, if this difference is above that value, the system displays a first-order phase transition. In the second system, we consider a linear correlation between the natural frequencies and the degrees of the nodes in Erdr˝os-Rénly and scale-free networks. The Hubs in this system have a natural frequency which are very different from the natural frequency of his neighbors. We use annealed network approximation and compare with our simulations. We demonstrate that the system undergoes a second-order phase transition for Erdr˝os-Rénly networks and scale-free networks with degree exponent > 3, and a first-order phase transition for scale-free networks with 2 < < 3.
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McClean, Colin John. "The scale-free and scale-bound properties of land surfaces : fractal analysis and specific geomorphometry from digital terrain models." Thesis, Durham University, 1990. http://etheses.dur.ac.uk/5999/.
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The scale-bound view of landsurfaces, being an assemblage of certain landforms, occurring within limited scale ranges, has been challenged by the scale-free characteristics of fractal geometry. This thesis assesses the fractal model by examining the irregularity of landsurface form, for the self-affine behaviour present in fractional Brownian surfaces. Different methods for detecting self-affine behaviour in surfaces are considered and of these the variogram technique is shown to be the most effective. It produces the best results of two methods tested on simulated surfaces, with known fractal properties. The algorithm used has been adapted to consider log (altitude variance) over a sample of log (distances) for: complete surfaces; subareas within surfaces; separate directions within surfaces. Twenty seven digital elevation models of landsurfaces arc re-examined for self- affine behaviour. The variogram results for complete surfaces show that none of these are self-affine over the scale range considered. This is because of dominant slope lengths and regular valley, spacing within areas. For similar reasons subarea analysis produces the non-fractal behaviour of markedly different variograms for separate subareas. The linearity of landforms in many areas, is detected by the variograms for separate directions. This indicates that the roughness of landsurfaces is anisotropic, unlike that of fractal surfaces. Because of difficulties in extracting particular landforms from their landsurfaces, no clear links between fractal behaviour, and landform size distribution could be established. A comparative study shows the geomorphometric parameters of fractal surfaces to vary with fractal dimension, while the geomorphometry of landsurfaces varies with the landforms present. Fractal dimensions estimated from landsurfaces do not correlate with geomorphometric parameters. From the results of this study, real landsurfaces would not appear to be scale- free. Therefore, a scale-bound approach towards landsurfaces would seem to be more appropriate to geomorphology than the fractal alternative.
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Mönch, Christian. "Distances in preferential attachment networks." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607617.
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Preferential attachment networks with power law degree sequence undergo a phase transition when the power law exponent τ changes. For τ > 3 typical distances in the network are logarithmic in the size of the network and for 2 < τ < 3 they are doubly logarithmic. In this thesis, we identify the correct scaling constant for τ ∈ (2, 3) and discover a surprising dichotomy between preferential attachment networks and networks without preferential attachment. This contradicts previous conjectures of universality. Moreover, using a model recently introduced by Dereich and Mörters, we study the critical behaviour at τ = 3, and establish novel results for the scale of the typical distances under lower order perturbations of the attachment function.
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Yilmazsoy, Baris. "netQ : a scale for measuring user perceptions of free, virtual-only service experience." Thesis, University of the West of England, Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500783.
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Organisations are continuously under the pressure of change, which is often stimulated and shaped by technology nowadays. Change impacts individuals' perceptions of the world, their needs and expectations. Inevitably, in an everchanging environment, organisations have to adapt their products and offerings and implement strategies to better understand the beliefs, attitudes, intentions and behaviours of their customers. Quite possible the biggest change we have witnessed in the last two decades was the emergence of the Internet. This, coupled with the digitalisation of data and the globalisation of business, created both opportunities and threats to bricks and mortar organisations and enabled the burst of dotcom companies. New products and services appeared, while the existing ones were reshaped. Similar to the traditional context, delivering superior service online appears to be prerequisite for success. However, knowing what 'superior service' means for the users of the service is not straightforward. Knowing the factors affecting users' service quality assessments is critical. In the absence of objective measures, service quality can be measured through users' perceptions of quality. This is where marketing scales come into play.
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Chan, Ho-yin, and 陳浩賢. "Semi-analytical and numerical studies on the dynamics of scale-free complex network." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B43754569.
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Chan, Ho-yin. "Semi-analytical and numerical studies on the dynamics of scale-free complex network." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43754569.
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Vest, Jeffrey D. "Robust, location-free scale estimators for the linear regression and k-sample models." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-151058/.
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Girardin, Bertrand. "Numerical modelling and small scale testing of fire performances for halogen-free cables." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10030/document.
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L'objectif de ce travail de thèse est d’étudier le comportement au feu de câbles électriques par deux approches, la première consistant à développer des méthodes de caractérisation des propriétés des gaines externes de câbles afin d’en modéliser le comportement au feu. Parallèlement, une approche basée sur le développement d’un banc d'essai original à échelle réduite a été étudiée. La caractérisation des propriétés thermo-physique des matériaux a permis la prédiction de la température et de la perte de masse lors d'expériences thermogravimétriques, de gazéification et de combustion. Il a été montré que tester de mince spécimen de gaine de câbles dans une enceinte à échelle réduite permettait la prédiction des résultats de la norme EN 50399. Ce nouveau test de l'échelle du laboratoire a ensuite utilisé avec succès pour le développement de nouveaux câbles présentant des propriétés feu amélioréesThe aim of this PhD work is to study the behavior of cables following two approaches: numerical modelling and small scale testing. First, methodologies to characterize the properties of the cables jacket materials were developed to further model their fire behavior. Concurrently, an approach was followed by developing a novel bench-scale fire test. Innovative methodologies using simultaneous thermal analyzer, Hot Disc apparatus were developed and so, the thermo-physical properties of the materials were characterized both as a function of temperature and of the decomposition state. Using these parameters as inputs data for a pyrolysis model, the temperature and mass loss rate were well predicted in case of thermo-gravimetric experiments, gasification and mass loss calorimeter. Moreover, it was shown that testing thin specimen of cables jacket materials in a reduced scaled enclosure of the EN 50399 test allowed the prediction of the results obtained on the large scale test carried out on whole cables. This new bench scale test was then successfully to develop new material that can be used as jacket for halogen-free electrical cable
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Li, Dezhi. "Properties and behaviour of Pb-free solders in flip-chip scale solder interconnections." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/34206.
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Due to pending legislations and market pressure, lead-free solders will replace Sn–Pb solders in 2006. Among the lead-free solders being studied, eutectic Sn–Ag, Sn–Cu and Sn–Ag–Cu are promising candidates and Sn–3.8Ag–0.7Cu could be the most appropriate replacement due to its overall balance of properties. In order to garner more understanding of lead-free solders and their application in flip-chip scale packages, the properties of lead free solders, including the wettability, intermetallic compound (IMC) growth and distribution, mechanical properties, reliability and corrosion resistance, were studied and are presented in this thesis.
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Martin, Damian. "Effects of high intensity, large-scale free-stream turbulence on combustor effusion cooling." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/14725.
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Full-coverage or effusion cooling is commonly used in the thermal management of gas turbine combustion systems. The combustor environment is characterised by highly turbulent free-stream conditions and relatively large turbulent length scales. This turbulent flow field is predominantly created by the upstream fuel injector for lean burn systems. In rich burn systems the turbulent flow field is augmented further by the addition of dilution ports. The available evidence suggests that large energetic eddies interact strongly with the injected coolant fluid and may have a significant impact on the film-cooling performance. The desire to create compact low-emission combustion systems with improved specific fuel consumption, has given rise to a desire to reduce the quantity of air used in wall cooling, and has led to the need for improved cooling correlations and validated computational methods. In order to establish a greater understanding of effusion cooling under conditions of very high free-stream turbulence, a new laboratory test facility has been created that is capable of simulating representative combustor flow conditions, and that allows for a systematic investigation of cooling performance over a range of free-stream turbulence conditions (up to 25% intensity, integral length scale-to-coolant hole diameter ratios of 26) and coolant to mainstream density ratios (??_c/??_??? ???2). This thesis describes this new test facility, including the method for generating combustor relevant flow conditions. The hot side film cooling performance of cylindrical and fanned hole effusion has been evaluated in terms of adiabatic film-cooling effectiveness and normalised heat transfer coefficient (HTC) and heat flux reduction (HFR). Infrared thermography was employed to produce spatial resolved surface temperature distributions of the effusion surface. The analysis of this data is supported by fluid temperature field measurements. The interpretation of the data has established the impact of turbulence intensity, integral length scale and density ratio on the mixing processes between free-stream and coolant flows. Elevated levels of free-stream turbulence increase the rate of mixing and degrade the cooling effectiveness at low blowing ratios whereas at high blowing ratios, where the coolant detaches from the surface, a modest increase has been observed under certain conditions; this is due to the turbulent transport of the detached coolant fluid back towards the wall. For angled cylindrical hole injection the impact of density ratio as an independent parameter was found to be relatively weak. Adiabatic effectiveness data gathered at DR's of 1 - 1.4 scaled reasonable well when plotted against momentum flux ratio. This suggests data collected at low DR's can be scaled to engine representative DR's. The investigation of shaped cooling holes found fanned effusion has the potential to dramatically improve film effectiveness. The diffusion of the flow through a fanned exit prevented jet detachment at blowing ratios up to 5, increasing spatially averaged effectiveness by 89%.
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Dubuis, Benoît Dubuis Benoît Dubuis Benoît Dubuis Benoît. "Design and scale-up of bubble-free fluidised bed reactors for plant cell cultures /." Zürich : [s.l.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10649.
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Ford, Elizabeth. "Barabási-Albert random graphs, scale-free distributions and bounds for approximation through Stein's method." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:b1091661-33b5-47fe-912c-61286159904a.
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Barabási-Albert random graph models are a class of evolving random graphs that are frequently used to model social networks with scale-free degree distributions. It has been shown that Barabási-Albert random graph models have asymptotic scale-free degree distributions as the size of the graph tends to infinity. Real world networks, however, have finite size so it is important to know how close the degree distribution of a Barabási-Albert random graph of a given size is to its asymptotic distribution. Stein’s method is chosen as one main method for obtaining explicit bounds for the distance between distributions. We derive a new version of Stein’s method for a class of scale-free distributions and apply the method to a Barabási-Albert random graph. We compare the evolution of a sequence of Barabási-Albert random graphs with continuous time stochastic processes motivated by Yule’s model for evolution. Through a coupling of the models we bound the total variation distance between their degree distributions. Using these bounds, we extend degree distribution bounds that we find for specific models within the scheme to find bounds for every member of the scheme. We apply the Azuma-Hoeffding inequality and Chernoff bounds to find bounds between the degree sequences of the random graph models and the given scale-free distribution. These bounds prove that the degree sequences converge completely (and therefore also converge almost surely) to our scale-free distribution. We discuss the relationship between the random graph processes and the Chinese restaurant process. Aided by the construction of an inhomogeneous Markov chain, we apply our results for the degree distribution in a Barabási-Albert random graph to a particular statistic of the Chinese restaurant process. Finally, we explore how our methods can be adapted and extended to other evolving random graph processes. We study a Bernoulli evolving random graph process, for which we bound the distance between its degree distribution and a geometric distribution and we bound the distance between the number of triangles in the graph and a normal distribution.
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Roark, Sean Howard. "Comparison of free-vortex wake models for a sub-scale rotor at low speeds." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7802.
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Thesis (M.S.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Hackley, Jason. "A Liquid-Helium-Free High-Stability Cryogenic Scanning Tunneling Microscope for Atomic-Scale Spectroscopy." Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19211.
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This dissertation provides a brief introduction into scanning tunneling microscopy, and then Chapter III reports on the design and operation of a cryogenic ultra-high vacuum scanning tunneling microscope (STM) coupled to a closed-cycle cryostat (CCC). The STM is thermally linked to the CCC through helium exchange gas confined inside a volume enclosed by highly flexible rubber bellows. The STM is thus mechanically decoupled from the CCC, which results in a significant reduction of the mechanical noise transferred from the CCC to the STM. Noise analysis of the tunneling current shows current fluctuations up to 4% of the total current, which translates into tip-sample distance variations of up to 1.5 picometers. This noise level is sufficiently low for atomic-resolution imaging of a wide variety of surfaces. To demonstrate this, atomic-resolution images of Au(111) and NaCl(100)/Au(111) surfaces, as well as of carbon nanotubes deposited on Au(111), were obtained. Other performance characteristics such as thermal drift analysis and a cool-down analysis are reported. Scanning tunneling spectroscopy (STS) measurements based on the lock-in technique were also carried out and showed no detectable presence of noise from the CCC. These results demonstrate that the constructed CCC-coupled STM is a highly stable instrument capable of highly detailed spectroscopic investigations of materials and surfaces at the atomic-scale.
A study of electron transport in single-walled carbon nanotubes (SWCNTs) was also conducted. In Chapter IV, STS is used to study the quantum-confined electronic states in SWCNTs deposited on the Au(111) surface. The STS spectra show the vibrational overtones which suggest rippling distortion and dimerization of carbon atoms on the SWCNT surface. This study experimentally connects the properties of well-defined localized electronic states to the properties of their associated vibronic states.
In Chapter V, a study of PbS nanocrystals was conducted to study the effect of localized sub-bandgap states associated with surface imperfections. A correlation between their properties and the atomic-scale structure of chemical imperfections responsible for their appearance was established to understand the nature of such surface states.
This dissertation includes both previously published/unpublished and co-authored material.
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Kumalo, Molefi Petrus. "Characterization of sheep and goat production systems amongst small-scale farmers in the Southern Free State." Thesis, Bloemfontein : Central University of Technology, Free State, 2014. http://hdl.handle.net/11462/266.
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Cirnigliaro, Giulio. "Progettazione ed implementazione di strumenti per la valutazione di reti complesse con proprietà scale-free." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2664/.
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Il cervello è una rete di cellule nervose connesse da assoni e le cellule stesse sono reti di molecole connesse da reazioni biochimiche. Anche le società sono reti di persone collegate da rapporti di amicizia, parentela e legami professionali. Su più larga scala, catene alimentari ed ecosistemi possono essere rappresentati come reti di specie viventi. E le reti pervadono la tecnologia: Internet, reti elettriche e sistemi di trasporto non sono che pochi degli esempi possibili. Anche il linguaggio che si sta usando in questo momento per veicolare questi ragionamenti a chi legge è una rete, fatta di parole connesse da relazioni sintattiche. A dispetto dell'importanza e della pervasività delle reti, gli scienziati hanno sempre avuto poca comprensione delle loro strutture e proprietà. In che
modo le interazioni di alcuni nodi non funzionanti in una complessa rete genetica possono generare il cancro? Come può avvenire così rapidamente la diffusione in taluni sistemi sociali e di comunicazioni, portando ad epidemie
di malattie e a virus informatici? Come possono alcune reti continuare a funzionare anche dopo che la maggioranza dei loro nodi ha, invece, smesso di farlo? [...] Le reti reali sono realmente casuali?
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Dogan, Eda. "Effects of large-scale free stream turbulence on a zero-pressure-gradient turbulent boundary layer." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/412650/.
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The focus of this study is to investigate the characteristics of a zero-pressure-gradient turbulent boundary layer in the presence of large-scale free-stream turbulence. Particular attention is given to scale interactions occurring within the turbulent boundary layer. The free-stream turbulence was generated by an active grid. The investigation was conducted as an experimental work using hot-wire anemometry and Particle Image Velocimetry. Large-scale structures occurring in the free-stream are shown to penetrate the boundary layer and increase the streamwise velocity fluctuations throughout. The near-wall peak amplitude of the streamwise velocity fluctuations are observed to increase with increasing turbulence level in the free-stream. This trend has been found analogous to high Reynolds number flows for increasing ? . Free-stream turbulence imposes an outer energy peak in the boundary layer and the energy level of this peak is observed to increase with increasing turbulence level. It is also shown that the large-scales dominating the outer region of the boundary layer have a modulating effect on the small-scales in the near wall region; this effect becomes more significant with increasing turbulence level in the free-stream. These added up to the analogy between the high Reynolds number flows and present study cases. The latest efforts in the field of high Reynolds number flow investigations are aimed towards predicting the near-wall turbulence using only the large-scale information input. Therefore, this analogy has encouraging implications towards generalising large-scale influences on the near-wall small scales. The study also presents results regarding the structural organisation inside the boundary layer using the PIV data. The coherent structures found inside the boundary layer are observed to have inclined features as consistent with the previous studies for canonical flows. The fact that the external disturbance, such as FST in this study, does not alter the organisation of the structures inside the boundary layer could potentially provide an evidence for a universal structure for all wall-bounded flows as also proposed from previous studies in the literature.
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Righi, Giovanni Gaspare. "Proprietà statistiche delle caratteristiche topologiche del grafo di un "hub" generato da un social network." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amslaurea.unibo.it/820/.
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Questa tesi affronta lo studio delle proprietà statistiche della topologia di un grafo, che rappresenta le relazioni interpersonali in un gruppo di utenti di Facebook. Perché è interessante? Quali informazioni produce? Anzitutto va osservato che dalla nascita di Internet in poi la globalizzazione ha reso le relazioni sociali un fenomeno di massa con numeri sorprendentemente alti di connessioni. Questo e la disponibilità dei dati forniscono una occasione preziosa per analizzarne la struttura.
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Zilber, Nicolas. "ERF and scale-free analyses of source-reconstructed MEG brain signals during a multisensory learning paradigm." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00984990.
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The analysis of Human brain activity in magnetoencephalography (MEG) can be generally conducted in two ways: either by focusing on the average response evoked by a stimulus repeated over time, more commonly known as an ''event-related field'' (ERF), or by decomposing the signal into functionally relevant oscillatory or frequency bands (such as alpha, beta or gamma). However, the major part of brain activity is arrhythmic and these approaches fail in describing its complexity, particularly in resting-state. As an alternative, the analysis of the 1/f-type power spectrum observed in the very low frequencies, a hallmark of scale-free dynamics, can overcome these issues. Yet it remains unclear whether this scale-free property is functionally relevant and whether its fluctuations matter for behavior. To address this question, our first concern was to establish a visual learning paradigm that would entail functional plasticity during an MEG session. In order to optimize the training effects, we developed new audiovisual (AV) stimuli (an acoustic texture paired with a colored visual motion) that induced multisensory integration and indeed improved learning compared to visual training solely (V) or accompanied with acoustic noise (AVn). This led us to investigate the neural correlates of these three types of training using first a classical method such as the ERF analysis. After source reconstruction on each individual cortical surface using MNE-dSPM, the network involved in the task was identified at the group-level. The selective plasticity observed in the human motion area (hMT+) correlated across all individuals with the behavioral improvement and was supported by a larger network in AV comprising multisensory areas. On the basis of these findings, we further explored the links between the behavior and scale-free properties of these same source-reconstructed MEG signals. Although most studies restricted their analysis to the global measure of self-similarity (i.e. long-range fluctuations), we also considered local fluctuations (i.e. multifractality) by using the Wavelet Leader Based Multifractal Formalism (WLBMF). We found intertwined modulations of self-similarity and multifractality in the same cortical regions as those revealed by the ERF analysis. Most astonishing, the degree of multifractality observed in each individual converged during the training towards a single attractor that reflected the asymptotic behavioral performance in hMT+. Finally, these findings and their associated methodological issues are compared with the ones that came out from the ERF analysis.
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Galanova, Yekaterina (Katherine) Yur'Yevna. "An Exploration of Altruistic Behavior of Substance-Abuse Facilities According to Their Ownership Status." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc103317/.
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Using the 2009 National Survey of Substance Abuse Treatment Services (N-SSATS), this paper uses logistic regressions to explore the effect of facility ownership on a facility’s show of altruism. Facility’s show of altruism is operationalized as a facility offering free treatment to all its clients, free treatment to some of its clients, or a facility offering a sliding fee scale to its client base in order to absorb some of the cost of treatment based on a potential client's income. Region, receipt of public funds, and religious affiliation are added as covariates in order to gauge whether the potential relationship between facility ownership and a facility’s show of altruism is genuine. Results indicate that private, for-profit ownership status of a facility is associated with a lower likelihood that a substance-abuse treatment facility would engage in altruistic behavior. However, receipt of public funds acts as a mediating variable, in that, its inclusion raises the likelihood that a private, for-profit facility would engage in shows of altruism. Furthermore, it appears that religious-affiliation increases the likelihood that a facility would display altruism by providing free treatment, to some of its clients, or to all, but less likely to display altruism by employing a sliding fee scale. Overall, inclusion of region, receipt of public funds, and religious affiliation all produce statistically significant results, along with facility ownership. This suggests that there are a variety of variables, apart from facility ownership alone, that might be influential over a facility's show of altruism.
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Janson, Alexander, and Snickare Erik. "Examining the structure of the KTH web." Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-186373.
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This thesis studies the characteristics of the network structure extracted from the public KTH web. The network structure was extracted with a crawler and consisted of 671,013 nodes and 23,515,683 links. The system is studied by applying statistical concepts from network science such as degree distribution and average path to reveal the characteristics of the network. The aim of the statistical analysis is to explore the robustness of the network and to answer if the network is scale-free. The thesis will examine the results from the study and compare the results to previous similar research. The results indicate that there might have been a change in regards to the network structure of websites since the last major research was done on the subject, likely caused by changes in web design. However, the results still indicate characteristics typical for a scale-free network. Due to irregularities in the crawler results may be slightly unreliable.Detta kandidatexamensarbete undersöker de egenskaper i nätverksstrukturen för det allmänna KTH nätet. Denna struktur extraherades med en spindel och bestod av 671,013 noder och 23,515,583 länkar. Systemet studerades genom att applicera statistiska koncept från nätverksteori såsom gradfördelning och genomsnittlig väg för att visa nätverkets egenskaper. Målet med den statistiska undersökningen är utforska nätverkets robusthet och besvara frågan om nätverket är så kallad scale-free. Studien jämför även resultaten med resultat från tidigare studier med liknande undersökningar. Resultaten indikerar att det kan ha blivit en förändring i avseende på nätverkets struktur sedan den tidigare omfattande studien genomfördes, förmodligen orsakat av ändringar i webdesign. Trots det så indikerar resultaten att nätverket fortfarande har egenskaper typiska för ett scale-free nätverk. På grund av oregelbundenhet i spindeln så kan resultaten vara smått opålitliga.
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Sherwood, Patricia Ann. "Inspections : software development process for building defect free software applied in a small-scale software development environment /." Online version of thesis, 1990. http://hdl.handle.net/1850/10598.
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Martinez, Rivas Adrian. "Wafer scale integration of coulomb blockade-based nanobiosensors with microfluidic channels for label-free detection of cancer biomarkers." Toulouse, INSA, 2009. http://eprint.insa-toulouse.fr/archive/00000344/.
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In this thesis we propose and implement the fabrication on 4 inch wafer of a novel type of nanobiosensor capable of high sensitivity detection. The principle of the nanobiosensor is based on the variation of electrical tunnelling conductivity through metal nanoislands due to the quantum phenomenon called “Coulomb blockade”. Nickel nanoislands (~5nm diameter), are placed between interdigitated nanoelectrodes devices (IND) (width~45nm). Hence, the conductivity of these Multiple-Tunnel-Junction (MTJ) devices is modified by the adsorption of biomarkers involved in tumourigenesis. Oncologists have recently isolated and characterised a new conformational single chain variable fragment (scFv) which selectively recognises the active form of RhoA. This potential biomarker has been found overexpressed in various tumours. Antibodies fragments (scFv) are adsorbed through coordinative bonds onto nickel nanoislands. Hence the scFv are capable of recognising specifically the active RhoA conformation. We have investigated this biomarker and validated the nickel nanoilands based chemical construction for label-free biodetection using a quartz crystal microbalance (QCM) before implementing the methodology to our devices. An innovative methodology to realise photoPDMS-based microchannels was also developed. Encapsulation with an etched PDMS-nanocomposite finalised the integration of the devices. The final electrical characterisation of the integrated device was tested in real time and continuous biological flow. The active form of RhoA was discriminated against its inactive conformation. In annexe, I present my epistemological and ethical opinions in nanotechnologyDans cette thèse, nous proposons et démontrons un nouveau type de nanobiocapteur pour la détection de biomolécules à haute sensibilité et leur intégration à grande échelle (plaquette de 4 pouces). Le principe du nouveau nanobiocapteur électrique est basé sur la variation de conductivité électrique à travers des nano-îlots grâce au phénomène quantique appelé « blocage de Coulomb ». Les nano-îlots de nickel (~5nm de diamètre) sont placés entre les nano-électrodes interdigitées (IND) (~45nm de largeur). La conductivité de ces dispositifs à Jonctions Tunnel Multiples (MTJ) est modifiée par l’adsorption de biomarqueurs impliqués dans la tumorogènese. Les oncologues ont récemment isolé et caractérisé un nouveau fragment d’anticorps à chaîne simple (scFv) qui reconnaît sélectivement la forme active de RhoA. Ce biomarqueur potentiel a été trouvé surexprimé dans diverses tumeurs. Les fragments d’anticorps ont été adsorbés, par des liaisons de coordination, sur les nano-îlots de nickel. Ces fragments sont capables de reconnaître spécifiquement la forme active de RhoA. Nous avons étudié ce biomarqueur et validé la chimie de surface à base de nano-’îlots de nickel pour la détection sans marquage, en utilisant une microbalance à quartz (QCM). Puis, nous avons mis au point et adapté à notre dispositif une méthodologie innovatrice pour réaliser, à l’échelle d’une plaquette, des microcanaux basés sur du photoPDMS. La caractérisation électrique finale des dispositifs intégrés a été testée en temps réel et à flux biologique continu. La forme active de RhoA a été détectée en discriminant la forme inactive. En annexe, je présente mon opinion épistémologique et éthique sur la nanotechnologie
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Ervine, Richard Blair. "The development of a free-running, scale model of a Cape-Island type fisheries patrol vessel for broaching tests." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0010/MQ31569.pdf.
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König, Lars [Verfasser]. "Matrix-free approaches for deformable image registration with large-scale and real-time applications in medical imaging / Lars König." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2019. http://d-nb.info/1175137189/34.
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Otiaba, Kenny C. "Thermal and thermo-mechanical performance of voided lead-free solder thermal interface materials for chip-scale packaged power device." Thesis, University of Greenwich, 2013. http://gala.gre.ac.uk/11391/.
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The need to maximise thermal performance of electronic devices coupled with the continuing trends on miniaturization of electronic packages require innovative package designs for power devices and modules such as Electronic Control Unit (ECU). Chip scale packaging (CSP) technology offer promising solution for packaging power electronics. This is as a result of the technology’s relatively improved thermal performance and inherent size advantage. In CSP technology, heat removal from the device could be enhanced through the backside of the chip. Heat dissipating units such as heat spreader and/or heat sink can be attached to the backside (reverse side) of the heat generating silicon die (via TIM) in an effort to improve the surface area available for heat dissipation. TIMs are used to mechanically couple the heat generating chip to a heat sinking device and more crucially to enhance thermal transfer across the interface. Extensive review shows that solder thermal interface materials (STIMs) apparently offer better thermal performance than comparable state-of-the-art commercial polymer-based TIMs and thus a preferable choice in packaging power devices. Nonetheless, voiding remains a major reliability concern of STIMs. This is coupled with the fact that solder joints are generally prone to fatigue failures under thermal cyclic loading. Unfortunately, the occurrence of solder voids is almost unavoidable during manufacturing process and is even predominant in lead (Pb)-free solder joints. The impacts of these voids on the thermal and mechanical performance of solder joints are not clearly understood and scarcely available in literature especially with regards to STIMs (large area solder joints). Hence, this work aims to investigate STIM and the influence of voids on the thermo-mechanical and thermal performance of STIM. As previous results suggest that factors such as the location, configuration (spatial arrangement) and size of voids play vital roles on the exact effect of voids, extensive three dimensional (3D) finite element modelling is employed to elucidate the precise effect of these void features on a Pb-free STIM selected after thermo-mechanical fatigue test of standard Pb-free solder alloys. Finite element analysis (FEA) results show that solder voids configuration, size and location are all vital parameters in evaluating the mechanical and thermal impacts of voids. Depending on the location, configuration and size of voids; solder voids can either influence the initiation or propagation of damage in the STIM layer or the location of hot spot on the heat generating chip. Experimental techniques are further employed to compare and correlate levels of voiding and shear strength for representative Pb-free solders. Experimental results also suggest that void size, location and configuration may have an influence on the mechanical durability of solder joints. The findings of this research work would be of interest to electronic packaging engineers especially in the automotive sector and have been disseminated through publications in peer reviewed journals and presentations in international conferences.