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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Lyapunov Exponents for Random Dynamical Systems

Thai Son, Doan 27 November 2009 (has links)
In this thesis the Lyapunov exponents of random dynamical systems are presented and investigated. The main results are: 1. In the space of all unbounded linear cocycles satisfying a certain integrability condition, we construct an open set of linear cocycles have simple Lyapunov spectrum and no exponential separation. Thus, unlike the bounded case, the exponential separation property is nongeneric in the space of unbounded cocycles. 2. The multiplicative ergodic theorem is established for random difference equations as well as random differential equations with random delay. 3. We provide a computational method for computing an invariant measure for infinite iterated functions systems as well as the Lyapunov exponents of products of random matrices. / In den vorliegenden Arbeit werden Lyapunov-Exponented für zufällige dynamische Systeme untersucht. Die Hauptresultate sind: 1. Im Raum aller unbeschränkten linearen Kozyklen, die eine gewisse Integrabilitätsbedingung erfüllen, konstruieren wir eine offene Menge linearer Kyzyklen, die einfaches Lyapunov-Spektrum besitzen und nicht exponentiell separiert sind. Im Gegensatz zum beschränkten Fall ist die Eingenschaft der exponentiellen Separiertheit nicht generisch in Raum der unbeschränkten Kozyklen. 2. Sowohl für zufällige Differenzengleichungen, als auch für zufällige Differentialgleichungen, mit zufälligem Delay wird ein multiplikatives Ergodentheorem bewiesen. 3.Eine algorithmisch implementierbare Methode wird entwickelt zur Berechnung von invarianten Maßen für unendliche iterierte Funktionensysteme und zur Berechnung von Lyapunov-Exponenten für Produkte von zufälligen Matrizen.
142

Fragment Based Protein Active Site Analysis Using Markov Random Field Combinations of Stereochemical Feature-Based Classifications

Pai Karkala, Reetal 2009 May 1900 (has links)
Recent improvements in structural genomics efforts have greatly increased the number of hypothetical proteins in the Protein Data Bank. Several computational methodologies have been developed to determine the function of these proteins but none of these methods have been able to account successfully for the diversity in the sequence and structural conformations observed in proteins that have the same function. An additional complication is the flexibility in both the protein active site and the ligand. In this dissertation, novel approaches to deal with both the ligand flexibility and the diversity in stereochemistry have been proposed. The active site analysis problem is formalized as a classification problem in which, for a given test protein, the goal is to predict the class of ligand most likely to bind the active site based on its stereochemical nature and thereby define its function. Traditional methods that have adapted a similar methodology have struggled to account for the flexibility observed in large ligands. Therefore, I propose a novel fragment-based approach to dealing with larger ligands. The advantage of the fragment-based methodology is that considering the protein-ligand interactions in a piecewise manner does not affect the active site patterns, and it also provides for a way to account for the problems associated with flexible ligands. I also propose two feature-based methodologies to account for the diversity observed in sequences and structural conformations among proteins with the same function. The feature-based methodologies provide detailed descriptions of the active site stereochemistry and are capable of identifying stereochemical patterns within the active site despite the diversity. Finally, I propose a Markov Random Field approach to combine the individual ligand fragment classifications (based on the stereochemical descriptors) into a single multi-fragment ligand class. This probabilistic framework combines the information provided by stereochemical features with the information regarding geometric constraints between ligand fragments to make a final ligand class prediction. The feature-based fragment identification methodology had an accuracy of 84% across a diverse set of ligand fragments and the mrf analysis was able to succesfully combine the various ligand fragments (identified by feature-based analysis) into one final ligand based on statistical models of ligand fragment distances. This novel approach to protein active site analysis was additionally tested on 3 proteins with very low sequence and structural similarity to other proteins in the PDB (a challenge for traditional methods) and in each of these cases, this approach successfully identified the cognate ligand. This approach addresses the two main issues that affect the accuracy of current automated methodologies in protein function assignment.
143

Capacity Proportional Unstructured Peer-to-Peer Networks

Reddy, 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.
144

Analysis of Entropy Levels in the Entropy Pool of Random Number Generator / Analysis of Entropy Levels in the Entropy Pool of Random Number Generator

Krempa, Peter January 2013 (has links)
V informatice je pojem entropie obvykle znám jako nahodný proud dat.  Tato práce krátce shrnuje metody generovaní nahodných dat a popisuje generátor náhodnych čísel, jež je obsažen v jádře operačního systému Linux.  Dále se práce zabývá určením bitové rychlosti generování nahodných dat tímto generátorem ve virtualizovaném prosředí, které poskytují různé hypervizory.  Práce popíše problémy nízkého výkonu generátory nahodných dat ve virtualním prostředí a navrhne postup pro jejich řešení.  Poté je nastíňena implementace navržených postupů, které je podrobena testům a její vysledky jsou porovnány s původním systémem. Systém pro distribuci entropie může dále vylepšit množství entropie v sytémovém jádře o několik řádu, pokud je připojen k vykonému generátoru nahodných dat.
145

Randomisation, sphères et déplacements de robots

Devillers, Olivier 23 November 1993 (has links) (PDF)
Ce mémoire d'habilitation présente 14 articles différents, structurés en trois parties : algorithmes randomisés, algorithmes sur les sphères et placements de robots.<br /><br />Les algorithmes randomisés ont été un des sujets ``chauds'' de ces dernières années et nous proposons ici des travaux ayant trait à des algorithmes dynamiques ou semi-dynamiques : tout d'abord un schéma général d'algorithmes semi-dynamiques avec des applications aux diagrammes de Voronoï, aux diagrammes de Voronoï d'ordre k aux arrangements, et ensuite deux algorithmes dynamiques (permettant d'insérer et de supprimer des données) pour la triangulation de Delaunay et le calcul d'un arrangement de segments. D'autres résultats concernent des algorithmes statiques, notamment le calcul du squelette d'un polygone simple en temps O(n log* n).<br /><br />La deuxième partie explore différentes modélisations des sphères. On peut en déduire notamment un algorithme en O(tk log n) pour la triangulation de Delaunay de n points appartenant à k plans en 3 dimensions, si t désigne la taille du résultat; dans la cas de deux plans cet algorithme atteint une complexité optimale de O(t+n log n). Nous proposons également un algorithme de complexité O(n^ ceil(d/2) +n log n) pour le calcul de l'enveloppe convexe de n sphères en dimension d, et un algorithme optimal (quadratique) pour le calcul de la surface de Connolly.<br /><br />La dernière partie traite de problèmes spécifiques à la planification de trajectoires, un premier chapitre concerne le cas de plusieurs robots polygonaux en translation dans le plan: certaines configurations appellées double-contacts peuvent jouer un rôle particulier dans certains cas. Ensuite deux résultats à propos de robots à pattes : l'analyse d'un cas simple que nous avons baptisé robot araignée, et l'étude de la stabilité d'un robot un peu plus complexe.
146

Pavages Aléatoires / Random Tilings

Ugolnikova, Alexandra 02 December 2016 (has links)
Dans cette thèse nous étudions deux types de pavages : des pavages par une paire de carres et des pavages sur le réseau tri-hexagonal (Kagome). Nous considérons différents problèmes combinatoires et probabilistes. Nous commençons par le cas des carres 1x1 et 2x2 sur des bandes infinies de hauteur k et obtenons des résultats sur la proportion moyenne des carres 1x1 pour les cas planaire et cylindrique pour k < 11. Nous considérons également des questions échantillonnage et comptage approximatif. Pour obtenir un échantillon aléatoire nous définissons des chaines de Markov pour les pavages par des carres et sur le réseau Kagome. Nous montrons des bornes polynomiales pour le temps de mélange pour les pavages par des carres 1x1 et sxs des régions n log net les pavages Kagome des régions en forme de losange. Nous considérons aussi des chaines de Markov avec des poids w sur les tuiles. Nous montrons le mélange rapide avec des conditions spécifiques sur w pour les pavages par des carres 1x1 et sxs et pavages Kagome. Nous présentons des simulations qui suggèrent plusieurs conjectures, notamment l'existence des régions gelées pour les pavages aléatoires par des carres et sur le réseau Kagome des régions avec des bords non plats. / In this thesis we study two types of tilings : tilings by a pair of squares and tilings on the tri-hexagonal (Kagome) lattice. We consider different combinatorial and probabilistic problems. First, we study the case of 1x1 and 2x2 squares on infinite stripes of height k and get combinatorial results on proportions of 1x1 squares for k < 11 in plain and cylindrical cases. We generalize the problem for bigger squares. We consider questions about sampling and approximate counting. In order to get a random sample, we define Markov chains for square and Kagome tilings. We show ergodicity and find polynomial bounds on the mixing time for nxlog n regions in the case of tilings by 1x1 and sxs squares and for lozenge regions in the case of restrained Kagome tilings. We also consider weighted Markov chains where weights are put on the tiles. We show rapid mixing with conditions on for square tilings by 1x1 and sxs squares and for Kagome tilings. We provide simulations that suggest different conjectures, one of which existence of frozen regions in random tilings by squares and on the Kagome lattice of regions with non flat boundaries.
147

What's in a name? A study of the correlation between donor giving trends and donor recognition

Book, Sean E. 06 April 2016 (has links)
<p> This project seeks to identify the impact of donor recognition practices upon acquisition and retention of individual donors within the Southern California theatre industry as a shift occurs in philanthropy trending away from corporate to individual gifts. </p><p> Drawing upon interviews with development professionals, cost and benefit analysis, and investigation of past donations, this project determines the effectiveness of current donor recognition structures that are commonly implemented without constant analysis of their performance. The objective of gathering practical data and understanding how and what motivates the average theatre donor, will determine future donor recognition approaches that can be implemented within the Theatre Arts Department. Additionally, the results of this study will inform the implementation of a donor wall for the CSULB Theatre Arts Department</p>
148

Livsvärlden i skolpraktiken - är det möjligt : Elevers tankar om Les Misérables

Book, Irene January 2012 (has links)
Abstract The purpose of this article was to examine how students learn French by integrating a multimode way of learning through literature, music, poetry, painting, reading, writing and IT in the classroom, in order to create understanding and motivation regarding the subject, but also a sense of cooperation and sensibility toward each one of the students Individual work. In the study of Victor Hugo’s novel Les Misérables as a tool for learning and deepen understanding about human values, the focus was laid on essentials questions such as the question of good and evil which is the major theme presented in the novel. The results showed that the students developed a vast interest in literature and human condition and made progress in French in both oral and written work but also acquired more knowledge about the French history.
149

Från samförstånd till konfrontation i den svenska utrikespolitiken? : En studie om svensk utrikespolitik mellan åren 1989-2000

Book, Martin January 2010 (has links)
This thesis aims at investigating the conflict development of Swedish foreign policy debates during 1989-2000. It is rather assumed that the Swedish foreign policy debates have been highly characterized by a large consensus. Despite that, there have been certain occurrences where the political parties have flushed into party struggle and shown disagreements over the party frontiers. This has raised questions about the range of conflict and consensus in such debates where I have studied the political parties' backchats. I have studied situations where the political parties replicate each other in order to investigate the range of consensus and controversy that exists within different foreign policy areas. The purpose has been to determine if Swedish foreign policy has undergone substantial changes during the 1990s and transformed into a more conflict-ridden foreign policy in contrast to earlier post-war era. The empirical analysis reveals that the foreign policy of Sweden has undergone minor changes over time. The period of 1990s consists of a larger amount consensus than conflict and more controversy within internationalistic issues instead of national interests issues during the post-war era. The parties that are most given to politicize within different foreign policy issues are the Social Democrats, the Moderate Party and the Left-wing Party during the 1990s.
150

Vom waldeckischen volkalied ...

Book, Max, January 1933 (has links)
Inaug.-diss.--Greifswald. / Lebenalauf. At head of title: Deutsche philologie. "Verzeichnis der bisher # gewordonen lieder der erwachsenen" (annotated list of 485 songs): p. 103-128. "Literaturvorzoichain": p. [viii]-ix.

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