Spelling suggestions: "subject:"talks"" "subject:"walks""
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Capacity Proportional Unstructured Peer-to-Peer NetworksReddy, Chandan Rama 2009 August 1900 (has links)
Existing methods to utilize capacity-heterogeneity in a P2P system either rely
on constructing special overlays with capacity-proportional node degree or use topology adaptation to match a node's capacity with that of its neighbors. In existing
P2P networks, which are often characterized by diverse node capacities and high
churn, these methods may require large node degree or continuous topology adaptation, potentially making them infeasible due to their high overhead. In this thesis,
we propose an unstructured P2P system that attempts to address these issues. We
first prove that the overall throughput of search queries in a heterogeneous network
is maximized if and only if traffic load through each node is proportional to its capacity. Our proposed system achieves this traffic distribution by biasing search walks
using the Metropolis-Hastings algorithm, without requiring any special underlying
topology. We then define two saturation metrics for measuring the performance of
overlay networks: one for quantifying their ability to support random walks and the
second for measuring their potential to handle the overhead caused by churn. Using
simulations, we finally compare our proposed method with Gia, an existing system
which uses topology adaptation, and find that the former performs better under all
studied conditions, both saturation metrics, and such end-to-end parameters as query
success rate, latency, and query-hits for various file replication schemes.
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A Simulation Study of Walks in Large Social GraphsAnwar, Shahed 05 November 2015 (has links)
Online Social Networks (OSNs) such as Facebook, Twitter, and YouTube are among the most popular sites on the Internet. Billions of users are connected through these sites, building strong and effective communities to share views and ideas, and make recommendations nowadays. Therefore, by choosing an appropriate user-base from billions of people is required to analyze the structure and key characteristics of the large social graphs to improve current systems and to design new applications. For this reason, node sampling technique plays an important role to study large-scale social networks. As a basic requirement, the sampled nodes and their links should possess similar statistical features of the original network, otherwise the conclusion drawn from the sampled network may not be appropriate for the entire population. Hence, good sampling strategies are key to many online social network applications. For instance, before introducing a new product or adding new feature(s) of a product to the online social network community, that specific new product or the additional feature has to be exposed to only a small set of users, who are carefully chosen to represent the complete set of users. As such, different random walk-based sampling techniques have been introduced to produce samples of nodes that not only are internally well-connected but also capture the statistical features of the whole network. Traditionally, walk-based techniques do not have the restriction on the number of times that a node can be re-visited while sampling. This may lead to an inefficient sampling method, because the walk may be "stuck" at a small number of high-degree nodes without being able to reach out to the rest of the nodes. A random walk, even after a large number of hops, may not be able to obtain a sampled network that captures the statistical features of the entire network.
In this thesis, we propose two walk-based sampling techniques to address the above problem, called K-Avoiding Random Walk (KARW) and Neighborhood-Avoiding Random Walk (NARW). With KARW, the number of times that a node can be re-visited is constrained within a given number K. With NARW, the random walk works in a "jump" fashion, since the walk starts outside of the N-hop neighborhood from the current node chosen randomly. By avoiding the current nodes neighboring area of level-N, NARW is expected to reach out the other nodes within the entire network quickly. We apply these techniques to construct multiple independent subgraphs from a social graph, consisting of 63K users with around a million connections between users collected from a Facebook dataset. By simulating our proposed strategies, we collect performance metrics and compare the results with the current state-of-the-art sampling techniques (Uniform Random Sampling, Random Walk, and Metropolis Hastings Random Walk). We also calculate some of the key statistical features (i.e., degree distribution, betweenness centrality, closeness centrality, modularity, and clustering coefficient) of the sampled graphs to get an idea about the network structures that essentially represent the original social graph. / Graduate / 0984 / shahed.anwar@gmail.com
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An empirical examination of the weak form martingale efficient market theory of security price behaviorFinkelstein, John Maxwell, 1941- January 1971 (has links)
No description available.
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Generating random absolutely continuous distributionsSitton, David E. R. 12 1900 (has links)
No description available.
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Probabilistic Methods for Discrete Labeling Problems in Digital Image Processing and AnalysisShen, Rui Unknown Date
No description available.
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Collapse transition of SARWs with hydrophobic interaction on a two dimensional latticeGaudreault, Mathieu. January 2007 (has links)
We study the collapse transition of a lattice based protein model including an explicit coarse-grained model of a solvent. This model accounts for explicit hydrophobic interactions, and it is studied by Monte Carlo simulation. The protein is modelled as self-avoiding random walk with nearest neighbor interactions on a two dimensional lattice. Without the solvent, universal quantities of the chain around the collapse transition temperature are well known. Hydrophobicity is then modelled through a lattice of solvent molecules in which each molecule can have Q states depending of an orientation variable. Only one state is energetically favored, when two neighboring solvent molecules are both in the same state of orientation. The monomers are placed in interstitial position of the solvent lattice, and are only allowed to occupy sites surrounded by solvent cells of the same orientation. The potential of mean force between two interstitial solute molecules is calculated, showing a solvent mediated attraction typical of hydrophobic interactions. We then show that this potential increases with the energy of hydrogen bond formation as it appears in the model, while its characteristic range decreases. More importantly, we show that the chain embedded in the solvent undergoes a collapse transition, with the temperature of the transition being shifted relative to that of the chain in isolation. We calculate several critical exponents near the collapse transition, and we observe that their values are not conserved in presence of the explicit solvent.
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Phase Transitions in Polymeric Systems: A Directed Walk StudyIliev, Gerasim K. 19 January 2009 (has links)
In this thesis several classes of directed paths are considered as models
of linear polymers in a dilute solution. We obtain the generating functions for
each model by considering factorization arguments.
Information about the polymer behaviour can be extracted from the
singularity structure of the associated generating functions.
By using modified versions of these models we study the adsorption and
localization of polymer molecules, the behaviour of polymers subject to
a tensile force, the effects of stiffness, as well as the behaviour of polymers
in confined geometries.
In each of these situations the resulting generating functions
contain at least two physical singularities. We identify the phase transitions
in these systems by a changeover in the dominant singularity of the generating
function.
In the study of localization and polymers subject to a force, we utilize both
homopolymer and random copolymer models. For copolymers, the physically
relevant properties are obtained by considering a quenched average of the
free energy over all possible monomer sequences. This procedure is intractable
even for the simplest models. By considering the Morita approximation for several
walk models we obtain results which give a bound on the corresponding features
of the quenched system.
We use a mapping between a simple model of duplex DNA and an adsorbing Motzkin
path in order to study the mechanical unzipping of duplex DNA. From this
model, we obtain force-temperature diagrams which show re-entrant
behaviour of the force. We also develop a simple low temperature theory to
describe the behaviour of the force close to T=0 and find that the shape
of the force-temperature curve is associated with entropy in the ground state
of the system.
We consider the effect of stiffness on polymer adsorption and find that
the phase transition is second order for all finite stiffness parameters.
For systems of polymers in confined geometries, we find that the behaviour of
the polymer depends on the distance between the confining surfaces and
the associated interactions with each surface. In this problem, there exist
regimes where the polymer exerts a force on the surfaces which can be
attractive, repulsive or zero.
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Evaluating and applying contaminant transport models to groundwater systems /Purczel, Carl Leslie. January 2001 (has links) (PDF)
Thesis (M.Sc.)--University of Adelaide, Dept. of Applied Mathematics, 2001. / "November 2001." Bibliography: leaves 128-130.
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Stochastic fluctuations far from equilibrium : statistical mechanics of surface growth /Chin, Chen-Shan, January 2002 (has links)
Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 106-114).
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Quantum walks and ground state problemsRichter, Peter C. January 2007 (has links)
Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Computer Science." Includes bibliographical references (p. 94-100).
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