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Islam, Md Kamrul. "Explainable link prediction in large complex graphs - application to drug repurposing." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0203.
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De nombreux systèmes complexes du monde réel peuvent être représentés par des graphes, où les nœuds représentent des entités et les liens des relations entre les paires de nœuds. La prédiction de liens (LP) est l'un des problèmes les plus intéressants et les plus anciens dans le domaine de l'exploration de graphes ; elle prédit la probabilité d'un lien entre deux nœuds non connectés. Cette thèse étudie le problème LP dans les graphes simples et les graphes de connaissances (KGs). La première partie de cette thèse se concentre sur le problème LP dans les graphes simples. Dans la première étude, des approches basées sur la similarité et sur l'encastrement sont évaluées et comparées sur des graphes simples de différents domaines. L'étude a également identifié la difficulté de fixer le seuil du score de similarité pour calculer la métrique de précision des approches basées sur la similarité et a proposé une nouvelle méthode pour calculer la métrique. Les résultats ont montré la supériorité attendue des approches basées sur l'intégration. Cependant, chaque approche basée sur la similarité s'est avérée compétitive sur des graphes aux propriétés spécifiques. Nous avons pu vérifier expérimentalement que les approches basées sur la similarité sont explicables mais manquent de généralisation, tandis que les approches basées sur l'encastrement sont générales mais non explicables. La deuxième étude tente de surmonter la limitation de l'inexplicabilité des approches basées sur l'encastrement en découvrant des connexions intéressantes entre elles et les approches basées sur la similarité. La troisième étude démontre comment les approches basées sur la similarité peuvent être assemblées pour concevoir une approche LP supervisée explicable. Il est intéressant de noter que l'étude montre des performances LP élevées pour l'approche supervisée sur différents graphes, ce qui est très satisfaisant. La deuxième partie de la thèse se concentre sur les LP dans les KGs. Un KG est représenté comme une collection de triplets RDF, (head,relation,tail) où les entités head et tail sont reliées par une relation spécifique. Le problème de LP dans un KG est formulé comme la prédiction de la tête ou de la queue manquante dans un triplet. La LP basée sur l'incorporation de KG est devenue très populaire ces dernières années, et la génération de triplets négatifs est une tâche importante dans les méthodes d'incorporation. La quatrième étude traite d'une nouvelle méthode appelée SNS pour générer des triplets négatifs de haute qualité. Nos résultats montrent une meilleure performance LP lorsque SNS est utilisé que lorsque d'autres méthodes d'échantillonnage négatif sont utilisées. La deuxième étude traite d'une nouvelle méthode d'extraction de règles neuro-symboliques et d'une stratégie d'abduction pour expliquer les LP par une approche basée sur l'intégration en utilisant les règles apprises. La troisième étude applique notre LP explicable pour développer une nouvelle approche de repositionnement des médicaments pour COVID-19. L'approche apprend un ensemble d'enchâssements d'entités et de relations dans un KG centré sur COVID-19 pour obtenir un meilleur enchâssement des éléments du graphe. Pour la première fois à notre connaissance, des méthodes de criblage virtuel sont ensuite utilisées pour évaluer les prédictions obtenues à l'aide des embeddings. L'évaluation moléculaire et les chemins explicatifs apportent de la fiabilité aux résultats de prédiction et sont de nouvelles méthodes complémentaires et réutilisables pour mieux évaluer les molécules proposées pour le repositionnement. La dernière étude propose une architecture distribuée pour l'apprentissage des KG embeddings dans des environnements distribués et parallèles. Les résultats révèlent que l'apprentissage dans l'environnement distribué proposé, par rapport à un apprentissage centralisé, réduit considérablement le temps de calcul des méthodes d'incorporation KG sans affecter les performances des LPMany real-world complex systems can be well-represented with graphs, where nodes represent objects or entities and links/relations represent interactions between pairs of nodes. Link prediction (LP) is one of the most interesting and long-standing problems in the field of graph mining; it predicts the probability of a link between two unconnected nodes based on available information in the current graph. This thesis studies the LP problem in graphs. It consists of two parts: LP in simple graphs and LP knowledge graphs (KGs). In the first part, the LP problem is defined as predicting the probability of a link between a pair of nodes in a simple graph. In the first study, a few similarity-based and embedding-based LP approaches are evaluated and compared on simple graphs from various domains. he study also criticizes the traditional way of computing the precision metric of similarity-based approaches as the computation faces the difficulty of tuning the threshold for deciding the link existence based on the similarity score. We proposed a new way of computing the precision metric. The results showed the expected superiority of embedding-based approaches. Still, each of the similarity-based approaches is competitive on graphs with specific properties. We could check experimentally that similarity-based approaches are fully explainable but lack generalization due to their heuristic nature, whereas embedding-based approaches are general but not explainable. The second study tries to alleviate the unexplainability limitation of embedding-based approaches by uncovering interesting connections between them and similarity-based approaches to get an idea of what is learned in embedding-based approaches. The third study demonstrates how the similarity-based approaches can be ensembled to design an explainable supervised LP approach. Interestingly, the study shows high LP performance for the supervised approach across various graphs, which is competitive with embedding-based approaches.The second part of the thesis focuses on LP in KGs. A KG is represented as a collection of RDF triples, (head,relation,tail) where the head and the tail are two entities which are connected by a specific relation. The LP problem in a KG is formulated as predicting missing head or tail entities in a triple. LP approaches based on the embeddings of entities and relations of a KG have become very popular in recent years, and generating negative triples is an important task in KG embedding methods. The first study in this part discusses a new method called SNS to generate high-quality negative triples during the training of embedding methods for learning embeddings of KGs. The results we produced show better LP performance when SNS is injected into an embedding approach than when injecting state-of-the-art negative triple sampling methods. The second study in the second part discusses a new neuro-symbolic method of mining rules and an abduction strategy to explain LP by an embedding-based approach utilizing the learned rules. The third study applies the explainable LP to a COVID-19 KG to develop a new drug repurposing approach for COVID-19. The approach learns ”ensemble embeddings” of entities and relations in a COVID-19 centric KG, in order to get a better latent representation of the graph elements. For the first time to our knowledge, molecular docking is then used to evaluate the predictions obtained from drug repurposing using KG embedding. Molecular evaluation and explanatory paths bring reliability to prediction results and constitute new complementary and reusable methods for assessing KG-based drug repurposing. The last study proposes a distributed architecture for learning KG embeddings in distributed and parallel settings. The results of the study that the computational time of embedding methods improves remarkably without affecting LP performance when they are trained in the proposed distributed settings than the traditional centralized settings
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Lehbab, Imène. "Problèmes métriques dans les espaces de Grassmann." Electronic Thesis or Diss., Mulhouse, 2023. http://www.theses.fr/2023MULH6508.
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Il s'agit d'une contribution dans le domaine de la géométrie métrique du plan projectif complexe CP2 et de la variété de Grassmann réelle des plans dans R6. On s'intéresse à l'étude de tous les p-uplets, p ≥ 3, de droites équiangulaires dans C3 et des p-uplets de plans équi-isoclins dans R6. Sachant que 9 est le nombre maximum de droites équiangulaires que l'on peut construire dans C3, on décrit une méthode qui permet de construire tous les p-uplets de droites équiangulaires pour tout pϵ[3,9]. En particulier, on construit dans C3 cinq classes de congruence de quadruplets de droites équiangulaires dont une dépend d'un paramètre réel ɣ que l'on étend à une famille infinie de sextuplets de droites équiangulaires dépendant du même paramètre réel ɣ. En outre, on donne les angles pour lesquels nos sextuplets s'étendent au-delà et jusqu'aux 9-uplets. On sait qu'il existe un p-uplet, p≥3, de plans équi-isoclins engendrant Rr, r≥4, de paramètre c, 0This work contributes to the field of metric geometry of the complex projective plane CP2 and the real Grassmannian manifold of the planes in R6. More specifically, we study all p-tuples, p ≥ 3, of equiangular lines in C3 or equidistant points in CP2, and p-tuples of equi-isoclinic planes in R6. Knowing that 9 is the maximum number of equiangular lines that can be constructed in C3, we develop a method to obtain all p-tuples of equiangular lines for all p ϵ [3,9]. In particular, we construct in C3 five congruence classes of quadruples of equiangular lines, one of which depends on a real parameter ɣ, which we extend to an infinite family of sextuples of equiangular lines depending on the same real parameter ɣ. In addition, we give the angles for which our sextuples extend beyond and up to 9-tuples. We know that there exists a p-tuple, p ≥ 3, of equi-isoclinic planes generating Rr, r ≥ 4, with parameter c, 0< c <1, if and only if there exists a square symmetric matrix, called Seidel matrix, of p × p square blocks of order 2, whose diagonal blocks are all zero and the others are orthogonal matrices in O(2) and whose smallest eigenvalue is equal to - 1/c and has multiplicity 2p-r. In this thesis, we investigate the case r=6 and we also show that we can explicitly determine the spectrum of all Seidel matrices of order 2p, p ≥ 3 whose off-diagonal blocks are in {R0, S0} where R0 and S0 are respectively the zero-angle rotation and the zero-angle symmetry. We thus show an unexpected link between some p-tuples of equi-isoclinic planes in Rr and simple graphs of order p
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Montanaro, William M. Jr. "Character Degree Graphs of Almost Simple Groups." Kent State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=kent1398345504.
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CRUCIANI, EMILIO. "Simple Randomized Distributed Algorithms for Graph Clustering." Doctoral thesis, Gran Sasso Science Institute, 2019. http://hdl.handle.net/20.500.12571/9951.
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Label Propagation Algorithms are a class of heuristics for the problem of graph clustering, i.e., the problem of detecting groups of nodes whose connections are dense within each group and sparse between the groups. At the onset, a label is assigned to each node of the graph; then, each node iteratively updates its label according to a function of the labels of its neighbors. Empirical studies show that, after only a few rounds, nodes in the same cluster share the same label while nodes in different clusters have different labels. Although they are widely used in practice given their simplicity, efficiency, and effectiveness, there is no theoretical foundation to explain why such simple algorithms are able to perform such a hard task. The absence of theoretical progress in the analysis of Label Propagation Algorithms is due to the lack of mathematical techniques for handling the interplay between the non-linearity of their update rule and the topology of the underlying graph.
In this thesis we contextualize Label Propagation Algorithms in the framework of computational dynamics, simple dynamical processes on networks whose behavior has been formally characterized on some classes of graphs. The analyses of computational dynamics were mainly focused on graphs with good connectivity properties, such as cliques or expanders, and on the problem of consensus, showing that they naturally converge to a configuration in which all the nodes agree on some value. We move a step forward in this direction by rigorously analyzing two simple dynamics, the 2-Choices dynamics and the Averaging dynamics, reaching a more fine-grained comprehension of their consensus behavior in classes of graphs that exhibit a clustered structure. In particular we formally prove that, with non-negligible probability, the two dynamics quickly bring the graph in a configuration where each cluster reaches an internal consensus on a value that is different among the clusters, and then enters a long metastable phase in which the internal consensus are maintained.
We show how to exploit such metastable behavior to design simple randomized distributed algorithms for graph clustering.
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Yan, Chenyu. "APPROXIMATING DISTANCES IN COMPLICATED GRAPHS BY DISTANCES IN SIMPLE GRAPHS WITH APPLICATIONS." Kent State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=kent1184639623.
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Kimmel, Jason. "Simple Games on Networks." Oberlin College Honors Theses / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1307994412.
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Okeke, Nnamdi, and University of Lethbridge Faculty of Arts and Science. "Character generators and graphs for simple lie algebras." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2006, 2006. http://hdl.handle.net/10133/532.
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We study character generating functions (character generators) of simple Lie algebras. The
expression due to Patera and Sharp, derived from the Weyl character formula, is ¯rst re-
viewed. A new general formula is then found. It makes clear the distinct roles of \outside"
and \inside" elements of the integrity basis, and helps determine their quadratic incompati-
bilities. We review, analyze and extend the results obtained by Gaskell using the Demazure
character formulas. We ¯nd that the fundamental generalized-poset graphs underlying the
character generators can be deduced from such calculations. These graphs, introduced by
Baclawski and Towber, can be simpli¯ed for the purposes of constructing the character
generator. The generating functions can be written easily using the simpli¯ed versions,
and associated Demazure expressions. The rank-two algebras are treated in detail, but we
believe our results are indicative of those for general simple Lie algebras.vii, 92 leaves ; 29 cm.
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Everett, Alistaire Duncan Fraser. "Commuting involution graphs of certain finite simple classical groups." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/commuting-involution-graphs-of-certain-finite-simple-classical-groups(dd54ee3d-8c94-42cd-87e1-d34770756466).html.
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For a group G and X a subset of G, the commuting graph of G on X, denoted by C(G,X), is the graph whose vertex set is X with x, y joined by an edge if x not equal to y and x and y commute. If the elements in X are involutions, then C(G,X) is called a commuting involution graph. This thesis studies C(G,X) when G is either a 4-dimensional projective symplectic group; a 3-dimensional unitary group; 4-dimensional unitary group over a field of characteristic 2; a 2-dimensional projective general linear group; or a 4-dimensional affne orthogonal group, and X a G-conjugacy class of involutions. We determine the diameters and structure of thediscs of these graphs.
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Bosi, Gianluca <1991>. "Simple random walks on some partially directed planar graphs." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/8914/1/bosi_gianluca_tesi.pdf.
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In this thesis we analyze the recurrence behavior of simple random walks on some classes of directed planar graphs. Our first model is a version of the honeycomb lattice, where the horizontal edges are randomly oriented according to families of random variables: depending on their distribution, we prove a.s. transience in some cases, and a.s. recurrence in other ones. Our results extend those obtained by Campanino and Petritis (’03 and ’14) for partially oriented square grid lattices.
Furthermore, we consider two directed square grid lattices on which, because of the direction imposed by the oriented edges, the simple random walk is bound to revolve clockwise: we prove recurrence for one of the graphs, solving a conjecture of Menshikov et al. (’17), and we give a new proof of transience for the other one.
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Mahfoudh, Mariem. "Adaptation d'ontologies avec les grammaires de graphes typés : évolution et fusion." Thesis, Mulhouse, 2015. http://www.theses.fr/2015MULH1519/document.
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Étant une représentation formelle et explicite des connaissances d'un domaine, les ontologies font régulièrement l'objet de nombreux changements et ont ainsi besoin d'être constamment adaptées pour notamment pouvoir être réutilisées et répondre aux nouveaux besoins. Leur réutilisation peut prendre différentes formes (évolution, alignement, fusion, etc.), et présente plusieurs verrous scientifiques. L'un des plus importants est la préservation de la consistance de l'ontologie lors de son changement. Afin d'y répondre, nous nous intéressons dans cette thèse à étudier les changements ontologiques et proposons un cadre formel capable de faire évoluer et de fusionner des ontologies sans affecter leur consistance. Premièrement, nous proposons TGGOnto (Typed Graph Grammars for Ontologies), un nouveau formalisme permettant la représentation des ontologies et leurs changements par les grammaires de graphes typés. Un couplage entre ces deux formalismes est défini afin de profiter des concepts des grammaires de graphes, notamment les NAC (Negative Application Conditions), pour la préservation de la consistance de l'ontologie adaptée.Deuxièmement, nous proposons EvOGG (Evolving Ontologies with Graph Grammars), une approche d'évolution d'ontologies qui se base sur le formalisme GGTOnto et traite les inconsistances d'une manière a priori. Nous nous intéressons aux ontologies OWL et nous traitons à la fois : (1) l'enrichissement d'ontologies en étudiant leur niveau structurel et (2) le peuplement d'ontologies en étudiant les changements qui affectent les individus et leurs assertions. L'approche EvOGG définit des changements ontologiques de différents types (élémentaires, composées et complexes) et assure leur implémentation par l'approche algébrique de transformation de graphes, SPO (Simple PushOut). Troisièmement, nous proposons GROM (Graph Rewriting for Ontology Merging), une approche de fusion d'ontologies capable d'éviter les redondances de données et de diminuer les conflits dans le résultat de fusion. L'approche proposée se décompose en trois étapes : (1) la recherche de similarité entre concepts en se basant sur des techniques syntaxiques, structurelles et sémantiques ; (2) la fusion d'ontologies par l'approche algébrique SPO ; (3) l'adaptation de l'ontologie globale résultante par le biais des règles de réécriture de graphes.Afin de valider les travaux menés dans cette thèse, nous avons développé plusieurs outils open source basés sur l'outil AGG (Attributed Graph Grammar). Ces outils ont été appliqués sur un ensemble d'ontologies, essentiellement sur celles développées dans le cadre du projet européen CCAlps (Creatives Companies in Alpine Space) qui a financé les travaux de cette thèseOntologies are a formal and explicit knowledge representation. They represent a given domain by their concepts and axioms while creating a consensus between a user community. To satisfy the new requirements of the represented domain, ontologies have to be regularly updated and adapted to maintain their consistency. The adaptation may take different forms (evolution, alignment, merging, etc.), and represents several scientific challenges. One of the most important is to preserve the consistency of the ontology during the changes. To address this issue, we are interested in this thesis to study the ontology changes and we propose a formal framework that can evolve and merge ontologies without affecting their consistency.First we propose TGGOnto (Typed Graph Grammars for Ontologies), a new formalism for the representation of ontologies and their changes using typed graph grammars (TGG). A coupling between ontologies and TGG is defined in order to take advantage of the graph grammars concepts, such as the NAC (Negative Application Conditions), in preserving the adapted ontology consistency. Second, we propose EvOGG (Evolving Ontologies with Graph Grammars), an ontology evolution approach that is based on the TGGOnto formalism that avoids inconsistencies using an a priori approach. We focus on OWL ontologies and we address both : (1) ontology enrichment by studying their structural level and (2) ontology population by studying the changes affecting individuals and their assertions. EvOGG approach defines different types of ontology changes (elementary, composite and complex) and ensures their implementation by the algebraic approach of graph transformation, SPO (Single pushout).Third, we propose GROM (Graph Rewriting for Ontology Merging), an ontologies merging approach that avoids data redundancy and reduces conflict in the merged result. The proposed approach consists of three steps: (1) the similarity search between concepts based on syntactic, structural and semantic techniques; (2) the ontologies merging by the algebraic approach SPO; (3) the global ontology adaptation with graph rewriting rules.To validate our proposals, we have developed several open source tools based on AGG (Attributed Graph Grammar) tool. These tools were applied to a set of ontologies, mainly on those developed in the frame of the CCAlps (Creatives Companies in Alpine Space) European project, which funded this thesis work
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Wright, Benjamin. "Graphs associated with the sporadic simple groups Fi₂₄ and BM." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/graphs-associated-with-the-sporadic-simple-groups-fi24-and-bm(dcdd493b-929d-4f91-a6bc-48c6b5fda3ba).html.
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Our aim is to calculate some graphs associated with two of the larger sporadicsimple groups, Fi₂₄ and the Baby Monster. Firstly we calculate the point line collinearity graph for a maximal 2-local geometry of Fi₂₄. If T is such a geometry, then the point line collinearity graph G will be the graph whose vertices are the points in T, with any two vertices joined by an edge if and only if they are incident with a common line. We found that the graph has diameter 5 and we give its collapsed adjacency matrix. We also calculate part of the commuting involution graph, C, for the class 2C of the Baby Monster, whose vertex set is the conjugacy class 2C, with any two elements joined by an edge if and only if they commute. We have managed to place all vertices inside C whose product with a fixed vertex t does not have 2 power order, with all evidence pointing towards C having diameter 3.
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Virotte-Ducharme, Marguerite-Marie. "Couples fischériens presque simples." Paris 7, 1985. http://www.theses.fr/1985PA077092.
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Frondana, Iara Moreira. "Model selection for discrete Markov random fields on graphs." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-02022018-151123/.
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In this thesis we propose to use a penalized maximum conditional likelihood criterion to estimate the graph of a general discrete Markov random field. We prove the almost sure convergence of the estimator of the graph in the case of a finite or countable infinite set of variables. Our method requires minimal assumptions on the probability distribution and contrary to other approaches in the literature, the usual positivity condition is not needed. We present several examples with a finite set of vertices and study the performance of the estimator on simulated data from theses examples. We also introduce an empirical procedure based on k-fold cross validation to select the best value of the constant in the estimators definition and show the application of this method in two real datasets.Nesta tese propomos um critério de máxima verossimilhança penalizada para estimar o grafo de dependência condicional de um campo aleatório Markoviano discreto. Provamos a convergência quase certa do estimador do grafo no caso de um conjunto finito ou infinito enumerável de variáveis. Nosso método requer condições mínimas na distribuição de probabilidade e contrariamente a outras abordagens da literatura, a condição usual de positividade não é necessária. Introduzimos alguns exemplos com um conjunto finito de vértices e estudamos o desempenho do estimador em dados simulados desses exemplos. Também propomos um procedimento empírico baseado no método de validação cruzada para selecionar o melhor valor da constante na definição do estimador, e mostramos a aplicação deste procedimento em dois conjuntos de dados reais.
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Matos, Jody Maick Araujo de. "Graph based algorithms to efficiently map VLSI circuits with simple cells." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/174523.
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Essa tese introduz um conjunto de algoritmos baseados em grafos para o mapeamento eficiente de circuitos VLSI com células simples. Os algoritmos propostos se baseiam em minimizar de maneira eficiente o número de elementos lógicos usados na implementação do circuito. Posteriormente, uma quantidade significativa de esforço é aplicada na minimização do número de inversores entre esses elementos lógicos. Por fim, essa representação lógica é mapeada para circuitos compostos somente por células NAND e NOR de duas entradas, juntamente com inversores. Células XOR e XNOR de duas entradas também podem ser consideradas. Como nós também consideramos circuitos sequenciais, flips-flops também são levados em consideração. Com o grande esforço de minimização de elementos lógicos, o circuito gerado pode conter algumas células com um fanout impraticável para os nodos tecnológicos atuais. Para corrigir essas ocorrências, nós propomos um algoritmo de limitação de fanout que considera tanto a área sendo utilizada pelas células quanto a sua profundidade lógica. Os algoritmos propostos foram aplicados sobre um conjunto de circuitos de benchmark e os resultados obtidos demonstram a utilidade dos métodos. Essa tese introduz um conjunto de algoritmos baseados em grafos para o mapeamento eficiente de circuitos VLSI com células simples. Os algoritmos propostos se baseiam em minimizar de maneira eficiente o número de elementos lógicos usados na implementação do circuito. Posteriormente, uma quantidade significativa de esforço é aplicada na minimização do número de inversores entre esses elementos lógicos. Por fim, essa representação lógica é mapeada para circuitos compostos somente por células NAND e NOR de duas entradas, juntamente com inversores. Células XOR e XNOR de duas entradas também podem ser consideradas. Como nós também consideramos circuitos sequenciais, flips-flops também são levados em consideração. Com o grande esforço de minimização de elementos lógicos, o circuito gerado pode conter algumas células com um fanout impraticável para os nodos tecnológicos atuais. Para corrigir essas ocorrências, nós propomos um algoritmo de limitação de fanout que considera tanto a área sendo utilizada pelas células quanto a sua profundidade lógica. Os algoritmos propostos foram aplicados sobre um conjunto de circuitos de benchmark e os resultados obtidos demonstram a utilidade dos métodos. Adicionalmente, algumas aplicações Morethan-Moore, tais como circuitos baseados em eletrônica impressa, também podem ser beneficiadas pela abordagem proposta.This thesis introduces a set of graph-based algorithms for efficiently mapping VLSI circuits using simple cells. The proposed algorithms are concerned to, first, effectively minimize the number of logic elements implementing the synthesized circuit. Then, we focus a significant effort on minimizing the number of inverters in between these logic elements. Finally, this logic representation is mapped into a circuit comprised of only two-input NANDs and NORS, along with the inverters. Two-input XORs and XNORs can also be optionally considered. As we also consider sequential circuits in this work, flip-flops are taken into account as well. Additionally, with high-effort optimization on the number of logic elements, the generated circuits may contain some cells with unfeasible fanout for current technology nodes. In order to fix these occurrences, we propose an area-oriented, level-aware algorithm for fanout limitation. The proposed algorithms were applied over a set of benchmark circuits and the obtained results have shown the usefulness of the method. We show that efficient implementations in terms of inverter count, transistor count, area, power and delay can be generated from circuits with a reduced number of both simple cells and inverters, combined with XOR/XNOR-based optimizations. The proposed buffering algorithm can handle all unfeasible fanout occurrences, while (i) optimizing the number of added inverters; and (ii) assigning cells to the inverter tree based on their level criticality. When comparing with academic and commercial approaches, we are able to simultaneously reduce the average number of inverters, transistors, area, power dissipation and delay up to 48%, 5%, 5%, 5%, and 53%, respectively. As the adoption of a limited set of simple standard cells have been showing benefits for a variety of modern VLSI circuits constraints, such as layout regularity, routability constraints, and/or ultra low power constraints, the proposed methods can be of special interest for these applications. Additionally, some More-than-Moore applications, such as printed electronics designs, can also take benefit from the proposed approach.
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Sander, Torsten [Verfasser]. "On simply structured bases of graph eigenspaces / Torsten Sander." [Clausthal-Zellerfeld] : [Univ.-Bibliothek], 2009. http://d-nb.info/997062517/34.
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KOUIDER-AISSA, MEKKIA. "Problemes de cycles, chaines et de decomposition de graphes simples." Paris 11, 1991. http://www.theses.fr/1991PA112396.
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Cette these comporte 3 chapitres suivant les differents sujets traites. Le chapitre i est le plus important, et traite de problemes de cycles. Il commence par une revue des resultats ou problemes concernant la decomposition ou la couverture par cycles de graphes simples; ensuite, nous traitons un probleme de couvertures par cycles de sommets d'un graphe simple (conjecture d'enomoto et al. ), puis nous avons etudie des conditions suffisantes d'existence de cycles de longueur superieure a une borne donnee (conjecture d'haggkvist) dans des graphes reguliers; enfin un probleme de couplage orthogonal a une 2-factorisation. Le chapitre ii traite du probleme de decomposition dans certaines familles de graphes simples en un nombre minimum de chaines (gallai), ou du probleme de decomposition en double-etoiles. Le chapitre iii concerne le probleme de la vulnerabilite et de la distance moyenne dans un reseau de communications (probleme de plesnik, conjecture de winkler)
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Fallahtoori, Sahar. "Distributed Graph Clustering: Study of DiDiC and Some Simpler Forms." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174831.
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The size of global electronic data in need of storage and retrieval is growing with an increasing rate. As a result of this growth, the development of technologies to process such data is a necessity. The data is developing in both complexity and connectivity, particularly for social networks. Connectivity of data means that the records to be stored are highly interdependent. Conventional relational databases are poorly suited for processing highly connected data. On the contrary, graph databases are inherently suited for such dependencies. This is mainly due to the fact that graph databases try to preserve locality and store adjacent records close to one another. This allows retrieval of adjacent elements, regardless of graph size, in constant time. Furthermore, with the everyday growth of data volume these databases won’t fit on single server any longer and need more (distributed) resources. Thus, partitioning of the data to be stored is required. Graph partitioning, based on its aim, can be divided into two major subcategories; a) Balanced partitioning where the aim is to find a predefined, N, number of equally sized clusters and b) Community detection where the aim is to find all underlying dense subgraphs. In this thesis we investigate and improve one particular graph partitioning algorithm, namely DiDiC, which is designed for balanced partitioning. DiDiC is short for diffusive and distributed graph partitioning. The algorithm is independently implemented in this thesis. The main testbeds of our work are real-world social network graphs such as Wikipedia or Facebook and synthetically generated graphs. DiDiC's various aspects and performance are further examined in different situations (i.e. types of graph) and using various sets of parameters (i.e. DiDiC hyperparameters). Our experiments indicate that DiDiC fails to partition the input graphs to the desired number of clusters in more than 70% of cases. In most failure cases it returns the whole graph as a single cluster. We noticed that the diffusive aspects of DiDiC is minimally constrained. Inspired by these observations, we propose two diffusive variants of the DiDiC to address this issue and consequently improve the success rate. This is done mainly by constraining the diffusive aspect of DiDiC. The modifications are straightforward to implement and can be easily incorporated into existing graph databases. We show our modifications consistently outperforms DiDiC with a margin of ~30% success rate in various scenarios. The different scenarios include various sizes of graphs, with different connectivity and structure of underlying clusters. Furthermore, we demonstrate the effectiveness 5 of DiDiC in discovering underlying high density regions of graph a.k.a. “community detection”. In fact, we show that it is more successful in “community detection” (60% success rate) than "balanced clustering" (35% success rate). Finally, we investigate the importance of random initialization of DiDiC algorithm. We observe, while different initialization (and keeping the best performing one) can help the final performance, there is a diminishing return when the algorithm is randomly initialized more than 4 times.
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González, Ruiz Jacobo Leonardo 502510, and Ruiz Jacobo Leonardo González. "Calculo del clique-width en graficas simples de acuerdo a su estructura." Tesis de doctorado, Universidad Autónoma del Estado de México, 2018. http://hdl.handle.net/20.500.11799/95286.
Full textAbstract:
El cálculo del cliquewidth, un número entero que es un invariante para gráficas, ha sido estudiado de manera activa, ya que existen problemas catalogados como NP-Completos que tienen complejidad baja si su representación en gráficas tiene cliquewidth acotado. De cierta manera este parametro mide la dificultad de descomponer una gráfica en una estructura llamada árbol (por su topología). La importancia de este invariante radica en que si un problema de gráficas puede ser acotado por ella entonces puede ser resuelto en tiempo polinomial según el teorema principal de Courcelle. Por otra parte el cliquewidth tiene una relación directa con el invariante tree-width con la distinción de que el primero es más general que el segundo. Para calcular este tipo de invariantes se han propuesto en la literatura diferentes procedimientos que dividen la gráfica original en subgráficas las cuales determinan la complejidad, por lo que en la investigación aquí reportada se ha utilizado una descomposición particular de una gráfica simple, la cual consiste en descomponer la gráfica en ciclos simples y árboles. Las gráficas que consisten de ciclos simples y árboles se denominan cactus, sobre las cuales hemos demostrado que el clique-width es menor o igual a 4 lo que mejora la cota establecida por la relación entre el clique-width y el invariante treewidth la cual establece que el cwd(G) ≤ 3·2twd(G)−1. De igual manera se han estudiado otro tipo de gráficas denominadas poligonales, formadas por polígonos con mismo número de lados los cuales comparten entre si una única arista; sobre este tipo de gráficas en esta investigación se ha demostrado que el cliquewidth es igual a 5, de igual manera mejorando la cota conocida por la relación de las invariantes mencionadas anteriormente. Finalmente, estudiando el comportamiento de operaciones de union de estas subgráficas se ha propuesto un método de aproximación para el cálculo del cliquewidth de una gráfica simple de manera general. El algoritmo esta basado en el clásico algoritmo de Disjktra que encuentra el camino mas corto entre dos vértices de una gráfica. Del planteamiento de los algoritmos mencionados anteriormente se obtuvo la publicación de tres artículos, en los que se incluye el desarrollo de las demostraciones para el cálculo del clique-width en los diferentes escenarios de estudio.CONACyT
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Silva, Allan Kardec Messias da. "O degree graph dos grupos alternados e de outros grupos simples." reponame:Repositório Institucional da UnB, 2013. http://repositorio.unb.br/handle/10482/13601.
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Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Matemática, 2013.Submitted by Luiza Silva Almeida (luizaalmeida@bce.unb.br) on 2013-07-17T20:41:38Z No. of bitstreams: 1 2013_AllanKardecMessiasdaSilva.pdf: 811006 bytes, checksum: d150f5332d05a0c2ccff34412c37b29f (MD5)
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O presente trabalho é uma introdução ao estudo de um grafo chamado Degree Graph. Este grafo é associado aos graus dos caracteres de um grupo nito no seguinte modo: os vértices são os primos que dividem os graus dos caracteres irredutíveis e dois vértices p; q são conexos com uma aresta se o grupo possui um caráter irredutível cujo grau é divisível pelo produto pq. O Degree Graph foi estudado inicialmente em grupos solúveis e apenas a pouco teve seus estudos avançados para grupos não solúveis. Donald L. White completou o estudo para grupos simples em 2009 com o artigo `Degree Graphs of Simple Groups', onde ele descreve para todos os grupos nitos simples os correspondentes Degree Graphs. Vamos neste trabalho mostrar estes estudos para todos os grupos alternados, e alguns grupos simples lineares, simpléticos e unitários. O principal resultado que vamos ilustrar em detalhes é o fato que, se n 9, o Degree Graph do grupo alternado An é um grafo completo. Este resultado usa uma conjectura de Alvis, provada por Barry e Ward. _______________________________________________________________________________________ ABSTRACT
The present work is an introduction to the study of a graph called Degree Graph. This graph is associated to the degrees of the characters of a nite group in the following way: the vertices are the primes that divide the degrees of the irreducible characters and two vertices p; q are connected with an edge if the group has an irreducible character whose degree is divisible the product pq. O Degree Graph was initially studied for soluble groups and only recently also for non soluble groups. In 2009 Donald L. White completed the study for simple groups in the paper `Degree Graph of Simple Groups', where he describes for all nite simple groups the corresponding Degree Graphs. In this work, we will illustrate these studies for all alternating groups and some simple linear, symplectic and unitary groups. The main result that we will describe in detail is the fact that if n 9, the Degree Graph of the alternating group An is a complete graph. This result makes use of a conjecture of Alvis, proved by Barry Ward.
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Bereczki, Márk. "Graph Neural Networks for Article Recommendation based on Implicit User Feedback and Content." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300092.
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Recommender systems are widely used in websites and applications to help users find relevant content based on their interests. Graph neural networks achieved state- of-the- art results in the field of recommender systems, working on data represented in the form of a graph. However, most graph- based solutions hold challenges regarding computational complexity or the ability to generalize to new users. Therefore, we propose a novel graph- based recommender system, by modifying Simple Graph Convolution, an approach for efficient graph node classification, and add the capability of generalizing to new users. We build our proposed recommender system for recommending the articles of Peltarion Knowledge Center. By incorporating two data sources, implicit user feedback based on pageview data as well as the content of articles, we propose a hybrid recommender solution. Throughout our experiments, we compare our proposed solution with a matrix factorization approach as well as a popularity- based and a random baseline, analyse the hyperparameters of our model, and examine the capability of our solution to give recommendations to new users who were not part of the training data set. Our model results in slightly lower, but similar Mean Average Precision and Mean Reciprocal Rank scores to the matrix factorization approach, and outperforms the popularity- based and random baselines. The main advantages of our model are computational efficiency and its ability to give relevant recommendations to new users without the need for retraining the model, which are key features for real- world use cases.Rekommendationssystem används ofta på webbplatser och applikationer för att hjälpa användare att hitta relevant innehåll baserad på deras intressen. Med utvecklingen av grafneurala nätverk nådde toppmoderna resultat inom rekommendationssystem och representerade data i form av en graf. De flesta grafbaserade lösningar har dock svårt med beräkningskomplexitet eller att generalisera till nya användare. Därför föreslår vi ett nytt grafbaserat rekommendatorsystem genom att modifiera Simple Graph Convolution. De här tillvägagångssätt är en effektiv grafnodsklassificering och lägga till möjligheten att generalisera till nya användare. Vi bygger vårt föreslagna rekommendatorsystem för att rekommendera artiklarna från Peltarion Knowledge Center. Genom att integrera två datakällor, implicit användaråterkoppling baserad på sidvisningsdata samt innehållet i artiklar, föreslår vi en hybridrekommendatörslösning. Under våra experiment jämför vi vår föreslagna lösning med en matrisfaktoriseringsmetod samt en popularitetsbaserad och en slumpmässig baslinje, analyserar hyperparametrarna i vår modell och undersöker förmågan hos vår lösning att ge rekommendationer till nya användare som inte deltog av träningsdatamängden. Vår modell resulterar i något mindre men liknande Mean Average Precision och Mean Reciprocal Rank poäng till matrisfaktoriseringsmetoden och överträffar de popularitetsbaserade och slumpmässiga baslinjerna. De viktigaste fördelarna med vår modell är beräkningseffektivitet och dess förmåga att ge relevanta rekommendationer till nya användare utan behov av omskolning av modellen, vilket är nyckelfunktioner för verkliga användningsfall.
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Kaykobad, M. Tanvir. "Transforming Plane Triangulations by Simultaneous Diagonal Flips." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40499.
Full textAbstract:
We explore the problem of transforming plane triangulations using simultaneous
diagonal flips. Wagner showed that any n-vertex plane triangulation can be transformed to any other plane triangulation on equal number of vertices using a finite
sequence of diagonal flips. Later on it has been established that O(n) individual flips
suffice to complete this transformation. Bose et al. showed that the transformation
can also be done in 4 × (
2 /
log 54/53
+ 2 /
log 6/5
) logn + 2 ≈ 327.1 log n simultaneous flips. This
bound is asymptotically tight.
We present two algorithms to improve the leading coefficient of this bound for
transforming any plane triangulation into any other. The first of the two algorithms
lowers this bound down to 4 × (
2 /
log 12/11
+ 2 /
log 9/7
) logn + 2 ≈ 85.8 log n. By processing
and preprocessing the interior and exterior of the triangulation’s Hamiltonian cycle
parallelly in an interlaced fashion, we make further improvement of the algorithm
from ≈ 327.1 log n down to 12 /
log 6/5
logn + 2 ≈ 45.6 log n.
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De, Saedeleer Julie. "The residually weakly primitive and locally two-transitive rank two geometries for the groups PSL(2, q)." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210037.
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The main goal of this thesis is a contribution to the classification of all incidence geometriesof rank two on which some group PSL(2,q), q a prime power, acts flag-transitively.
Actually we require that the action be RWPRI (residually weakly primitive) and (2T)1
(doubly transitive on every residue of rank one). In fact our definition of RWPRI requires
the geometry to be firm (each residue of rank one has at least two elements) and RC
(residually connected).
The main goal is achieved in this thesis.
It is stated in our "Main Theorem". The proof of this theorem requires more than 60pages.
Quite surprisingly, our proof in the direction of the main goal uses essentially the classification
of all subgroups of PSL(2,q), a famous result provided in Dickson’s book "Linear groups: With an exposition of the Galois field theory", section 260, in which the group is called Linear Fractional Group LF(n, pn).
Our proof requires to work with all ordered pairs of subgroups up to conjugacy.
The restrictions such as RWPRI and (2T)1 allow for a complete analysis.
The geometries obtained in our "Main Theorem" are bipartite graphs; and also locally 2-arc-transitive
graphs in the sense of Giudici, Li and Cheryl Praeger. These graphs are interesting in their own right because of
the numerous connections they have with other fields of mathematics.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Lapalut, Stéphane. "Sémantique formelle et spécifications algébriques du raisonnement sur les graphes conceptuels simples et étendus." Nice, 1997. http://www.theses.fr/1997NICE5148.
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Ces travaux présentent une approche de la formalisation du raisonnement sur les graphes conceptuels proposés par J. F. Sowa. Dans la première partie, nous situons l'état de l'art et relevons les problématiques existantes dans ce formalisme. Nous en déduisons deux principales directions de travail : l'établissement d'une sémantique formelle pour les graphes conceptuels et l'étude d'une approche de grammaire de graphe permettant la spécification puis l'implantation des règles d'inférence sur ces graphes. La deuxième partie reconsidère le formalisme des graphes simples et propose les bases nécessaires à l'étude de leur extension à la négation. La troisième partie étend les graphes simples aux graphes étendus, qui intègrent principalement la logique et les règles d'inférence du système B de Peirce. Une sémantique au sens de Tarski, basée sur une interprétation du support d'une base de graphe, est proposée pour les deux types de graphes, incluant la négation dans le cas des graphes étendus. L'introduction de la notion de séquent de graphe permet l'étude de la validité de chaque opération de transformation et d'inférence sur les graphes conceptuels simples et étendus décrits. Un modèle algébrique pour chaque type de graphes permet l'établissement d'un schéma de graphe au sens du langage de spécification de grammaire de graphe progrès, à partir desquels chaque opération sur les graphes est spécifiée par une règle de grammaire de graphe. Les systèmes de requêtes par projections et par déduction se formalisent par des machines de grammaire de graphes utilisant deux approches de grammaires de graphes simples et étendus, pour lesquelles deux algorithmes non-déterministes sont proposés
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Schuhmacher, Michael Verfasser], and Simone Paolo [Akademischer Betreuer] [Ponzetto. "Knowledge Graph Exploration for Natural Language Understanding in Web Information Retrieval / Michael Schuhmacher ; Betreuer: Simone Paolo Ponzetto." Mannheim : Universitätsbibliothek Mannheim, 2016. http://d-nb.info/1120302587/34.
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Schuhmacher, Michael [Verfasser], and Simone Paolo [Akademischer Betreuer] Ponzetto. "Knowledge Graph Exploration for Natural Language Understanding in Web Information Retrieval / Michael Schuhmacher ; Betreuer: Simone Paolo Ponzetto." Mannheim : Universitätsbibliothek Mannheim, 2016. http://d-nb.info/1120302587/34.
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Hérault, Laurent. "Réseaux de neurones récursifs pour l'optimisation combinatoire : application à la théorie des graphes et à la vision par ordinateur." Grenoble INPG, 1991. http://www.theses.fr/1991INPG0019.
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Cette these traite de la resolution de problemes d'optimisation tres complexes (np. Complets) par le biais de l'etude des systemes complexes artificiels qui imitent les systemes physiques et qui sont simules avec des reseaux neuromimetiques. La solution optimale est identifiee a un etat fondamental d'un systeme physique. Plusieurs techniques neuronales sont presentees pour approcher la solution optimale. Elles utilisent soit l'analyse canonique, soit l'analyse microcanonique, definies en mecanique statistique. Parmi ces methodes, nous presentons l'utilisation des reseaux de hopfield analogiques, le recuit simule, l'approximation du champ moyen, le recuit en champ moyen et le recuit microcanonique. Elles sont particulierement bien adaptees aux problemes de graphes qui traitent de coupure et de connectivite, de morphisme et d'extraction de sous-graphes possedant des proprietes extremales. Dans ce cadre, les problemes de k-partitionnement de graphe, de mise en correspondance de graphes, et d'extraction de la plus grande clique sont traites. Dans la derniere partie, nous abordons le probleme de groupement perceptif en vision par ordinateur. On montre que ce probleme se ramene, par le biais de la theorie de la gestalt definie en psychologie experimentale, a un probleme d'optimisation combinatoire soluble par reseaux de neurones
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Prado, Gerônimo Rodrigues. "Superfosfato simples contendo fosfato de ferro de baixa solubilidade aplicado em solos de várzea do Rio Grande do Sul." Universidade Federal de Santa Maria, 2009. http://repositorio.ufsm.br/handle/1/5499.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorSome rocks used in fertilizer production contain impurities of low solubility in water such as iron aluminum phosphate (Fe- Al- P). The use of these rocks generates simple superphosphate which may contain impurity levels that do not meet the fertilizer legislation in Brazil. One of the possibilities for the use of fertilizers containing high degree of impurities of iron phosphate would be to apply in flooded soils. Thus, the aims of this work were: a) to study the phosphorous behavior originating from the simple superphosphate containing impurities of iron phosphate with low solubility in water, when submitted to flooding conditions in different flooding soils from RS used for the cultivation of the rice; b) to study the efficiency of the use of phosphorus originating from fertilizers containing impurities of insoluble iron phosphates in water when compared to single superphosphates without residues of iron phosphates in rice plants (Oryza sativa). Six lowland soils were collected from different places in the State of Rio Grande do Sul: two soils in Santa Maria (Planossolo and Gleissolo) and the others in Santa Vitória do Palmar (Chernossolo); Uruguaiana (Chernossolo); Cachoeirinha (Gleissolo) and Pelotas (Planossolo). The soils were conditioned in 8 L plastic vases. The treatments were structured in a bifatorial 6x3 (six soils, two P sources, simple superphosphate and simple superpohosphate with (Fe-P) residues without P addition). In treatments with P, 100 mg P Kg-1 was added to the soil. A water layer was maintained at 5 cm of height in vases above the soil and the collection of the soil solution was carried out weekly. pH and redox potential were measured immediately after each collection of the solution and the reading of the amount of P, iron and manganese was done just after that. Forty five days after flooding, eight exemplars of rice cultivar IRGA 422 CL were transplanted to be cultivated for 45 more days. The yield of dry matter from aerial part, the P amount in the tissue and the calculation of the P amount absorbed were determined. The results showed an increase of pH and of the amount of P, iron and manganese as well as a decrease of Eh in all soils. The simple superphophate containing insoluble impurities of iron phosphate in water presented behavior similar to simple superphosphate without impurities when applied in soils of meadow from Rio Grande do Sul, evidencing its potential to be used in these soils Rio Grande do Sul, evidencing its potential to be used in these soils.
Algumas rochas utilizadas na produção de fertilizantes contêm impurezas de baixa solubilidade em água, destacando-se alguns fosfatos de ferro-alumínio (Fe-Al-P). A utilização destas rochas pode gerar superfosfato simples contendo essas impurezas o que não atende a legislação de fertilizantes no Brasil. Uma das possibilidades para o aproveitamento dos fertilizantes com grau elevado de impurezas de fosfato de ferro seria aplicá-los em solos alagados. Portanto, os objetivos do presente trabalho foram: a) estudar o comportamento do fósforo oriundo do superfosfato simples contendo impurezas de fosfatos de ferro com baixa solubilidade em água, quando submetidos a condições de alagamento em diferentes solos de várzea do RS usados para o cultivo do arroz; e b) estudar a eficiência da utilização do fósforo oriundo dos fertilizantes contendo impurezas de fosfatos de ferro insolúveis em água quando comparados a superfosfatos simples sem resíduos de fosfatos de ferro em plantas de arroz (Oryza sativa). Foram coletados seis solos de várzea, de diferentes locais do Estado do Rio Grande do Sul (RS), sendo dois solos na cidade de Santa Maria (Planossolo e Gleissolo) e um solo em cada uma das cidades de Santa Vitória do Palmar (Chernossolo); Uruguaiana (Chernossolo); Cachoeirinha (Gleissolo) e Pelotas (Planossolo). Os solos foram acondicionados em vasos plásticos de 8 L. Os tratamentos foram estruturados em um bifatorial 6x3 (seis solos, duas fontes de fósforo - superfosfato simples e superfosfato simples com resíduos de ferro - e testemunha sem P). Nos tratamentos com fósforo foi adicionado ao solo 100 mg de P kg-1 de solo. Uma lâmina de água foi mantida a 5 cm de altura nos vasos acima do solo e realizou-se a coleta da solução do solo, semanalmente. O pH e o potencial redox foram medidos imediatamente após cada coleta da solução e em laboratório se procedeu a determinação dos teores de fósforo, ferro e manganês. Transcorrido 45 dias de alagamento, foram transplantadas oito plântulas de arroz cultivar IRGA 422 CL para serem cultivadas por um período de mais 45 dias. Foi determinado a produção de matéria seca da parte aérea (MSPA), o teor de fósforo (P) no tecido e o cálculo da quantidade de P absorvido. Os resultados mostraram aumento no pH, redução do Eh e aumento dos teores de fósforo, ferro e manganês em todos os solos. O superfofasto simples contendo impurezas de fosfato de ferro insolúveis em água apresentou comportamento semelhante ao superfosfato simples sem impurezas quando aplicados nos solos de várzea do Rio Grande do Sul, evidenciando seu potencial para uso nestes solos.
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Shdeed, Edouard. "Contribution a l'etude des grandes deflexions elastoplastiques de structures simples soumises aux grandes impulsions de choc de grande energie." Nantes, 1987. http://www.theses.fr/1987NANT2014.
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Etude de la deflexion finale de portiques de differentes epaisseurs (3 et 5mm) en au4g recuit ou trempe et en acier e24, soumis a des chocs generes par le lancement de projectiles a des vitesses comprises entre 5 et 25m/s. Etude theorique de ce phenomene, basee sur le mode d'approximation technique du comportement rigide-plastique
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Mattos, Bruno Donadelli Trajano. "Cálculo de áreas sem o uso do Teorema Fundamental do Cálculo." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/55/55136/tde-02022018-090342/.
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Desenvolvemos uma estratégia natural e acessível aos estudantes do Ensino Médio para o cálculo de áreas planas sem as ferramentas mais avançadas do Cálculo Diferencial e Integral.We developed a natural strategy, achievable by high school students, for the computation of area of limited regions of the cartesian plane, without making use of more advanced resources of Differential and Integral Calculus.
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Shdeed, Edouard. "Contribution à l'étude des grandes délexions élasto-plastiques de structures simples soumises à des impulsions de choc de grande énergie." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37609935p.
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Biswas, Arindam. "Théorie des groupes approximatifs et ses applications." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS573.
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Dans la premier partie de cette thèse, nous étudions la structure des sous-groupes approximatifs dans les groupes metabéliens (groupes résolubles de classe de résolubilité 2) et montrons que si A est un tel sous-groupe K approximatif, il est K^⁰(r) contrôlée (au sens du Tao) par un groupe nilpotent où $ r désigne le rang de $ G=Fit (G) et Fit (G) $ est le sous-groupe de fitting de G. La deuxième partie est consacrée à l'étude de la croissance des ensembles dans GLn(Fq) où Fq est un corps fini. Nous montrons une borne sur le diamètre (par rapport à n'importe quel système des générateurs) pour tous sous-groupes simples finis de ce groupe. Si G est un groupe fini simple de type Lie de rang n, et son corps de base est de taille borné, le diamètre du graphe du Cayley Gamma (G;S) serait borné par exp (O (n (log n) ^ 3)) . Si la taille du corps fini Fq n'est pas borné, notre méthode donne une borne de q ^ {O (n ( log nq) ^ 3) pour le diamètre.Dans la troisième partie nous nous sommes intéressés à la croissance des ensembles dans les boucles de Moufang commutatifs. Ceux-ci sont les boucles commutatifs respectant les identités de Moufang mais sans être (nécessairement) associatifs. Nous montrons que, si les tailles des ensembles des associateurs sont bornées alors la croissance des sous-structures approximatifs dans ces boucles est similaire à celle des groupes ordinaires. De cette façon dans le cadre des boucles de moufang commutatifs finiment engendré on a un théorème de structure pour ses sous-boucles approximatifs.Mots-clefs -sous-groupes approximatifs, groupes résolubles, diamètres des groupes, boucles de moufang commutatifsIn the first part of this thesis, we study the structure of approximate subgroups inside metabelian groups (solvable groups of derived length 2) and show that if A is such a K-approximate subgroup, then it is K^(O(r)) controlled (in the sense of Tao) by a nilpotent group where r denotes the rank of G=Fit(G) and Fit(G) is the fitting subgroup of G.The second part is devoted to the study of growth of sets inside GLn(Fq) , where we show a bound on the diameter (with respect to any set of generators) for all finite simple subgroups of this group. What we have is - if G is a finite simple group of Lie type with rank n, and its base field has bounded size, then the diameter of the Cayley graph C(G; S) would be bounded by exp(O(n(logn)^3)). If the size of the base field Fq is not bounded then our method gives a bound of q^(O(n(log nq)3)) for the diameter.In the third part we are interested in the growth of sets inside commutative Moufang loops which are commutative loops respecting the moufang identities but without (necessarily)being associative. For them we show that if the sizes of the associator sets are bounded then the growth of approximate substructures inside these loops is similar to those in ordinary groups. In this way for the subclass of finitely generated commutative moufang loops we have a classification theorem of its approximate subloops
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Lissner, Simone [Verfasser], and Lutz [Akademischer Betreuer] Graeve. "Intrazelluläres Trafficking des intestinalen Anionenaustauschers Down-Regulated in Adenoma (DRA;SLC26A3) / Simone Lissner. Betreuer: Lutz Graeve." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2012. http://d-nb.info/1027353363/34.
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Luiz, Simone Weide. "ESTUDO COMPARATIVO DA AQUISIÇÃO DO /R/ NA POSIÇÃO DE ONSET SIMPLES POR CRIANÇAS DE DOIS MUNICÍPIOS DO RIO GRANDE DO SUL." Universidade Federal de Santa Maria, 2012. http://repositorio.ufsm.br/handle/1/6513.
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The purpose of this study is to determine and to compare the emergence and
acquisition of /R/ in simple onset, as well as the influence of linguistic and extralinguistic
variables during the acquisition of this phoneme by children who live in Santa Maria, RS,
Brazil and Crissiumal, RS, Brazil. The sample consisted of 76 interviews in Crissiumal
and 60 interviews in Santa Maria, a total of 136 subjects. The children were aged
between 1:6 and 4:2. The speech data from Santa Maria are from a database system
which contains speech samples of children with typical phonological development. The
database system was created through a research project. To collect data from
Crissiumal, the children should observe the thematic drawings, part of the Child s
Phonological Assessment (YAVAS; HERNANDORENA; LAMPRECHT, 1991) and they
should name the drawings to perceive the way they produce the /R/. The data were
analyzed in each age group to have an acquisition profile. After that, for the statistical
analyzes related to the linguistic variables preceding and following context, tonicity,
number of syllables and word position; and the extralinguistic variables age and sex, the
Statistical Program VARBRUL was used. This program is used in quantitative
variationist analysis and phonological acquisition. Through the data analysis, it was
possible to observe that the /R/ emerges when the children are 2:0 in Santa Maria and
when the children are 2:2 in Crissiumal. In Santa Maria the phoneme is acquired when
the children are 3:6 in initial onset and 3:4 in medial onset. In Crissiumal the phoneme is
acquired when the children are 4:2 in initial onset and 4:0 in medial onset. Besides, in
Santa Maria the statistical program selected the linguistic variables following context and
number of syllables in initial onset and the extralinguistic variable sex in initial and
medial onset. In Crissiumal, the linguistic variable tonicity was selected in initial onset
and the variable following context was selected in medial onset. From the collected data,
it is possible to verify that the children from Santa Maria acquire the phoneme earlier
than the children from Crissiumal. Another relevant aspect is that most linguistic and
extralinguistic variables affect the /R/ acquisition in different ways, according to the
dialectal variant which is used in the considered place.O objetivo geral deste estudo é determinar e comparar a aquisição e o surgimento do rforte em onset simples, bem como a influência das variáveis linguísticas e extralinguísticas na aquisição deste fonema por crianças residentes nos municípios de Santa Maria-RS e Crissiumal-RS. A amostra de fala utilizada na pesquisa é composta por 76 entrevistas em Crissiumal e 60 entrevistas em Santa Maria, com um total de 136 informantes. Os sujeitos possuem idades entre 1:6 e 4:2. Os dados de fala de Santa Maria são provenientes de um banco de dados que contém amostras de fala de crianças com desenvolvimento fonológico típico, o qual foi criado a partir da realização de um projeto de pesquisa. Para a coleta de dados em Crissiumal, foi solicitado que as crianças observassem desenhos temáticos, parte da Avaliação Fonológica da Criança (AFC) (YAVAS, HERNANDORENA & LAMPRECHT, 1991) e também que nomeassem as figuras para observar a forma como elas produzem o r-forte . Os dados foram analisados por faixa etária para se chegar a um perfil aquisitivo. Após, para as análises estatísticas em relação às variáveis linguísticas contexto precedente, contexto seguinte, tonicidade, número de sílabas e posição na palavra; e das variáveis extralinguísticas sexo e idade, contou-se com o apoio do Pacote Computacional VARBRUL, que é um pacote estatístico amplamente utilizado em análises quantitativas variacionistas e de aquisição fonológica. Através da análise dos dados, constatou-se que o /R/ surge aos 2:0 nas crianças residentes em Santa Maria e aos 2:2 nas crianças residentes em Crissiumal. Em Santa Maria, o fonema é considerado adquirido aos 3:6 em onset inicial e aos 3:4 em onset medial. Já em Crissiumal o fonema se estabiliza em onset inicial aos 4:2 e em onset medial aos 4:0. Além disso, em Santa Maria o programa estatístico selecionou as variáveis linguísticas contexto seguinte e número de sílabas em onset inicial e a variável extralinguística sexo, tanto em onset inicial quanto em onset medial. Em Crissiumal, a variável linguística tonicidade foi selecionada em onset inicial e a variável linguística contexto seguinte foi selecionada em onset medial. Concluindo, a partir dos dados coletados, é possível constatar que as crianças residentes em Santa Maria adquirem o /R/ mais cedo que em Crissiumal. Outro aspecto relevante é que a maioria das variáveis linguísticas e as variáveis extralinguísticas consideradas afetam a aquisição do /R/ de forma distinta, conforme a variante dialetal utilizada.
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Voivret, Charles. "Texture et comportement des matériaux granulaires à grande polydispersité." Phd thesis, Montpellier 2, 2008. http://www.theses.fr/2008MON20111.
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Ce travail de thèse est consacré à la modélisation et à l'étude numérique de la texture et du comportement mécanique des matériaux granulaires à grande polydispersité. La polydispersité est considérée en termes d'étalement et de courbure de la distribution de tailles. Afin d'aboutir à des distributions de tailles représentatives, une méthode de génération ainsi qu'un modèle de courbe granulométrique sont présentés. La mise en place de grands échantillons denses par une méthode géométrique a permis de réaliser une étude systématique de l'influence de la polydispersité sur la texture. Le comportement mécanique est étudié par simulations numériques discrètes sur la base de la méthode de Dynamique des Contacts. Les échantillons sont successivement soumis à une relaxation uniaxiale et à un cisaillement simple avec des conditions aux limites périodiques afin d'atteindre respectivement l'état d'équilibre statique et l'état stationnaire après un cisaillement long. Nos résultats montrent que la distribution uniforme par fraction volumique conduit à la compacité la plus élevée. Dans l'état stationnaire, la résistance au cisaillement est indépendante de la polydispersité. Une analyse systématique de la texture permet de montrer que cette propriété résulte, d'une part, de la compensation mutuelle entre les anisotropies des directions de contact et des longueurs des vecteurs branches et, d'autre part, du fait que les forces fortes sont essentiellement transmise à travers les plus grosses particules. Enfin, en présence de forces d'adhésion, la cohésion de Coulomb augmente avec l'étalement granulométriqueThis work is devoted to the numerical modeling of highly polydisperse granular materials in view of investigating the texture and mechanical behavior in quasi-static shearing. The polydispersity is modeled in terms of size span and curvature of the particle size distributions. A method is proposed to generate representative size distributions both in number and volume of size classes, and the accessible polydispersity parameters are determined for tractable number of particles. A geometrical method is used to construct large samples and to study the resulting texture in a systematic manner as a function of size distribution. These samples are then subjected to simple shear with periodic boundary conditions by means of the contact dynamics method. We show that: 1) The highest level of solid fraction corresponds to uniform distribution by particle volume fractions; 2) The shear strength in the steady state is independent of polydispersity; 3) A detailed analysis of the texture and force transmission indicates that this property results from the mutual compensation between the anisotropies of contact orientations and branch-vector lengths, and also from the fact that the strong force chains are mainly captured by the largest particles; 4) In the presence of adhesion between particles, the Coulomb cohesion increases with size span
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Voivret, Charles. "Texture et comportement des matériaux granulaires à grande polydispersité." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2008. http://tel.archives-ouvertes.fr/tel-00372125.
Full textAbstract:
Ce travail de thèse est consacré à la modélisation et à l'étude numérique de la texture et du comportement mécanique des matériaux granulaires à grande polydispersité. La polydispersité est considérée en termes d'étalement et de courbure de la distribution de tailles. Afin d'aboutir à des distributions de tailles représentatives, une méthode de génération ainsi qu'un modèle de courbe granulométrique sont présentés. La mise en place de grands échantillons denses par une méthode géométrique a permis de réaliser une étude systématique de l'influence de la polydispersité sur la texture. Le comportement mécanique est étudié par simulations numériques discrètes sur la base de la méthode de Dynamique des Contacts. Les échantillons sont successivement soumis à une relaxation uniaxiale et à un cisaillement simple avec des conditions aux limites périodiques afin d'atteindre respectivement l'état d'équilibre statique et l'état stationnaire après un cisaillement long. Nos résultats montrent que la distribution uniforme par fraction volumique conduit à la compacité la plus élevée. Dans l'état stationnaire, la résistance au cisaillement est indépendante de la polydispersité. Une analyse systématique de la texture permet de montrer que cette propriété résulte, d'une part, de la compensation mutuelle entre les anisotropies des directions de contact et des longueurs des vecteurs branches et, d'autre part, du fait que les forces fortes sont essentiellement transmise à travers les plus grosses particules. Enfin, en présence de forces d'adhésion, la cohésion de Coulomb augmente avec l'étalement granulométrique.
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Soames, Kieron, and Jonas Lind. "Detecting Cycles in GraphQL Schemas." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-156174.
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GraphQL is a database handling API created by Facebook, that provides an effective al-ternative to REST-style architectures. GraphQL provides the ability for a client to spec-ify exactly what data it wishes to receive. A problem with GraphQL is that the freedomof creating customized requests allows data to be included several times in the response,growing the response’s size exponentially. The thesis contributes to the field of GraphQLanalysis by studying the prevalence of simple cycles in GraphQL schemas. We have im-plemented a locally-run tool and webtool using Tarjan’s and Johnson’s algorithms, thatparses the schemas, creates a directed graph and enumerates all simple cycles in the graph.A collection of schemas was analysed with the tool to collect empirical data. It was foundthat 39.73 % of the total 2094 schemas contained at least one simple cycle, with the averagenumber of cycles per schema being 4. The runtime was found to be on average 11 mil-liseconds, most of which consisted of the time for parsing the schemas. It was found that44 out of the considered schemas could not be enumerated due to containing a staggeringamount of simple cycles. It can be concluded that it is possible to test schemas for cyclicityand enumerate all simple cycles in a given schema efficiently.
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Xu, Yongchao. "Tree-based shape spaces : definition and applications in image processing and computer vision." Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-00981623.
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In a large number of applications, the processing relies on objects or area of interests, and the pixel-based image representation is notwell adapted. These applications would benefit from a region-based processing. Early examples of region-based processing can be found in the area of image segmentation, such as the quad tree. Recently, in mathematical morphology, the connected operators have received much attention. They are region-based filtering tools that act by merging flat zones. They have good contour preservation properties in the sense that they do not create any new boundaries, neither do they shift the existing ones. One popular implementation for connected operators relies on tree-based image representations, notably threshold decomposition representations and hierarchical representations. Those tree-based image representations are widely used in many image processing and computer vision applications. Tree-based connected operators consist in constructing a set of nested or disjoint connected components, followed by a filtering of these connected components based on an attribute function characterizing each connected component. Finally, the filtered image is reconstructed from the simplified tree composed of the remaining connected components. In the work presented in this thesis, we propose to expand the ideas of tree-based connected operators. We introduce the notion of tree-based shape spaces, built from tree-based image representations. Many state-of-the-art methods relying on tree-based image representations consist of analyzing this shape space. A first consequence of this change of point of view is our proposition of a local feature detector, called the tree-based Morse regions (TBMR). It can be seen as a variant of the MSER method. The selection of TBMRs is based on topological information, and hence it extracts the regions independently of the contrast, which makes it truly contrast invariant and quasi parameters free. The accuracy and robustness of the TBMR approach are demonstrated by the repeatability test and by applications to image registration and 3D reconstruction, as compared to some state-of-the-art methods. The basic idea of the main proposition in this thesis is to apply connected filters on the shape space. Such a processing is called the framework of shape-based morphology. It is a versatile framework that deals with region-based image representations. It has three main consequences. 1) For filtering purpose, it is a generalization of the existing tree-based connected operators. Indeed, the framework encompasses classical existing connected operators by attributes. Besides, It also allows us to propose two classes of novel connected operators: shape-based lower/upper levelings and shapings. 2) This framework can be used to object detection/segmentation by selecting relevant points in the shape space. 3) We can also use this framework to transform the hierarchies using the extinction values, so that a hierarchical simplification or segmentation is obtained. Some applications are developed using the framework of shape-based morphology to demonstrate its usefulness. The applications of the shape-based filtering to retinal image analysis show that a mere filtering step that we compare to more evolved processings, achieves state-of-the-art results. An efficient shaping used for image simplification is proposed by minimizing Mumford-Shah functional subordinated to the topographic map. For object detection/segmentation, we proposed a context-based energy estimator that is suitable to characterize object meaningfulness. Last, we extend the hierarchy of constrained connectivity using the aspect of hierarchy transformation of constrained connectivity using the aspect ofhierarchy transformation.
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Le, Boudec Adrien. "Géométrie des groupes localement compacts. Arbres. Action !" Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112036.
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Dans le Chapitre 1 nous étudions les groupes localement compacts lacunaires hyperboliques. Nous caractérisons les groupes ayant un cône asymptotique qui est un arbre réel et dont l'action naturelle est focale. Nous étudions également la structure des groupes lacunaires hyperboliques, et montrons que dans le cas unimodulaire les sous-groupes ne satisfont pas de loi. Nous appliquons au Chapitre 2 les résultats précédents pour résoudre le problème de l'existence de points de coupure dans un cône asymptotique dans le cas des groupes de Lie connexes. Dans le Chapitre 3 nous montrons que le groupe de Neretin est compactement présenté et donnons une borne supérieure sur sa fonction de Dehn. Nous étudions également les propriétés métriques du groupe de Neretin, et prouvons que certains sous-groupes remarquables sont quasi-isométriquement plongés. Nous étudions dans le Chapitre 4 une famille de groupes agissant sur un arbre, et dont l'action locale est prescrite par un groupe de permutations. Nous montrons entre autres que ces groupes ont la propriété (PW), et exhibons des groupes simples au sein de cette famille. Dans le Chapitre 5 nous introduisons l'éventail des relations d'un groupe de type fini, qui est l'ensemble des longueurs des relations non engendrées par des relations plus courtes. Nous établissons un lien entre la simple connexité d'un cône asymptotique et l'éventail des relations du groupe, et donnons une grande classe de groupes dont l'éventail des relations est aussi grand que possibleIn Chapter 1 we investigate the class of locally compact lacunary hyperbolic groups. We characterize locally compact groups having one asymptotic cone that is a real tree and whose natural isometric action is focal. We also study the structure of lacunary hyperbolic groups, and prove that in the unimodular case subgroups cannot satisfy a law. We apply the previous results in Chapter 2 to solve the problem of the existence of cut-points in asymptotic cones for connected Lie groups. In Chapter 3 we prove that Neretin's group is compactly presented and give an upper bound on its Dehn function. We also study metric properties of Neretin's group, and prove that some remarkable subgroups are quasi-isometrically embedded. In Chapter 4 we study a family of groups acting on a tree, and whose local action is prescribed by some permutation group. We prove among other things that these groups have property (PW), and exhibit some simple groups in this family. In Chapter 5 we introduce the relation range of a finitely generated group, which is the set of lengths of relations that are not generated by relations of smaller length. We establish a link between simple connectedness of asymptotic cones and the relation range of the group, and give a large class of groups having a relation range as large as possible
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Barcellos, Junior Antonio Soares de. "Análise evolutiva da indústria de frigoríficos de produtos suínos no Rio Grande do Sul do ano de 1950 até o ano de 2004: declínio ou simples concentração de mercado?" Universidade do Vale do Rio do Sinos, 2006. http://www.repositorio.jesuita.org.br/handle/UNISINOS/2694.
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O objetivo global deste estudo é proceder à verificação da evolução do Setor de Frigoríficos de Produtos Suínos Gaúchos desde o ano de 1950 até o ano de 2004. Neste sentido, a partir do Modelo das 5 Forças de Porter, serão analisados os fatos ocorridos com este Setor Industrial, buscando compreender as razões que fizeram com que o número de empresas concorrentes tenha sofrido uma diminuição tão significativa no período de pouco mais de 50 anos, bem como, a busca do entendimento das possíveis razões de sucesso daquelas que permaneceram no mercado, e se encontram atualmente competindo e disputando acirradamente na busca de um melhor “market share”. Acredita-se que a estratégia adotada e a correta utilização dos recursos, combinados com variáveis externas, muitas vezes de difícil controle, provavelmente possam ser ingredientes importantes para a busca de uma resposta. O aprofundamento destas análises e seus desdobramentos, portanto, se constituem como o eixo central desta pesquisa
This study global objective is to procede the evolution check of Pig Products Freezer Sector from Rio Grande do Sul since 1950 to 2004. In this way, according to the Model of Porter’s 5 Powers, it will be analyzed the occurred facts with this Industrial Sector, looking for understanding not only the reasons which had made the number of contestant companies suffered a significant decreasing in the period around 50 years, but also, the possible success reasons from which continue in the market and find each other, nowadays, competing intensively on the search of a better market share.It is believe that the adopted strategy and the correct resources utilization, combined with external variables, many times with difficult control, probably can be important ingredients for the search of an answer. To make our knowledge deeper about this analysis and its branches, therefore, they constitute themselves as the central axis of this research
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Gueydan, Frédéric. "La transition fragile-ductile de la croûte continentale en extension : du terrain à la modélisation." Paris 6, 2001. http://www.theses.fr/2001PA066514.
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Gramfort, Alexandre. "Localisation et suivi d'activité fonctionnelle cérébrale en électro et magnétoencéphalographie: Méthodes et applications au système visuel humain." Phd thesis, Ecole nationale supérieure des telecommunications - ENST, 2009. http://tel.archives-ouvertes.fr/tel-00426852.
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Cette thèse est consacrée à l'étude des signaux mesurés par Electroencéphalographie (EEG) et Magnétoencéphalographie (MEG) afin d'améliorer notre compréhension du cerveau humain. La MEG et l'EEG sont des modalités d'imagerie cérébrale non invasives. Elles permettent de mesurer, hors de la tête, respectivement le potentiel électrique et le champ magnétique induits par l'activité neuronale. Le principal objectif lié à l'exploitation de ces données est la localisation dans l'espace et dans le temps des sources de courant ayant généré les mesures. Pour ce faire, il est nécessaire de résoudre un certain nombre de problèmes mathématiques et informatiques difficiles. La première partie de cette thèse part de la présentation des fondements biologiques à l'origine des données M/EEG, jusqu'à la résolution du problème direct. Le problème direct permet de prédire les mesures générées pour une configuration de sources de courant donnée. La résolution de ce problème à l'aide des équations de Maxwell dans l'approximation quasi-statique passe par la modélisation des générateurs de courants, ainsi que de la géométrie du milieu conducteur, dans notre cas la tête. Cette modélisation aboutit à un problème direct linéaire qui n'admet pas de solution analytique lorsque l'on considère des modèles de tête réalistes. Notre première contribution porte sur l'implémentation d'une résolution numérique à base d'éléments finis surfaciques dont nous montrons l'excellente précision comparativement aux autres implémentations disponibles. Une fois le problème direct calculé, l'étape suivante consiste à estimer les positions et les amplitudes des sources ayant généré les mesures. Il s'agit de résoudre le problème inverse. Pour ce faire, trois méthodes existent: les méthodes paramétriques, les méthodes dites de "scanning", et les méthodes distribuées. Cette dernière approche fournit un cadre rigoureux à la résolution de problème inverse tout en évitant de faire de trop importantes approximations dans la modélisation. Toutefois, elle impose de résoudre un problème fortement sous-contraint qui nécessite de fait d'imposer des a priori sur les solutions. Ainsi la deuxième partie de cette thèse est consacrée aux différents types d'a priori pouvant être utilisés dans le problème inverse. Leur présentation part des méthodes de résolution mathématiques jusqu'aux détails d'implémentation et à leur utilisation en pratique sur des tailles de problèmes réalistes. Un intérêt particulier est porté aux a priori induisant de la parcimonie et conduisant à l'optimisation de problèmes convexes non différentiables pour lesquels sont présentées des méthodes d'optimisation efficaces à base d'itérations proximales. La troisième partie porte sur l'utilisation des méthodes exposées précédemment afin d'estimer des cartes rétinotopiques dans le système visuel à l'aide de données MEG. La présentation porte à la fois sur les aspects expérimentaux liés au protocole d'acquisition jusqu'à la mise en oeuvre du problème inverse en exploitant des propriétés sur le spectre du signal mesuré. La contribution suivante ambitionne d'aller plus loin que la simple localisation d'activités par le problème inverse afin de donner accès à la dynamique de l'activité corticale. Partant des estimations de sources sur le maillage cortical, la méthode proposée utilise des méthodes d'optimisation combinatoires à base de coupes de graphes afin d'effectuer de façon robuste le suivi de l'activité au cours du temps. La dernière contribution de cette thèse porte sur l'estimation de paramètres sur des données M/EEG brutes non moyennées. Compte tenu du faible rapport signal à bruit, l'analyse de données M/EEG dites "simple essai" est un problème particulièrement difficile dont l'intérêt est fondamental afin d'aller plus loin que l'analyse de données moyennées en explorant la variabilité inter-essais. La méthode proposée utilise des outils récents à base de graphes. Elle garantit des optimisations globales et s'affranchit de problèmes classiques tels que l'initialisation des paramètres ou l'utilisation du signal moyenné dans l'estimation. L'ensemble des méthodes développées durant cette thèse ont été utilisées sur des données M/EEG réels afin de garantir leur pertinence dans le contexte expérimental parfois complexe des signaux réelles M/EEG. Les implémentations et les données nécessaires à la reproductibilité des résultats sont disponibles. Le projet de rétinotopie par l'exploitation de données de MEG a été mené en collaboration avec l'équipe du LENA au sein de l'hôpital de La Pitié-Salpêtrière (Paris).
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Santos, Adriana Goulart dos. "Estudo do comportamento resiliente de três solos da região de Campo Grande-MS e de relações entre o módulo de resiliência e resultados de ensaios de compressão simples." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/18/18137/tde-06102009-093939/.
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O conhecimento do módulo de resiliência (MR) é fundamental ao se projetar um pavimento, pois ele é necessário para o cálculo de tensões, deformações e deflexões nas suas camadas e subleito, bem como, a análise do desempenho do sistema. Embora ensaios de campo possam ser empregados para se determinar o MR, a grande maioria das pesquisas nesse sentido são desenvolvidas em laboratório, onde é possível um maior controle das condições da amostra, da aplicação de carregamento e medida dos deslocamentos. Porém, pela complexidade e alto custo dos ensaios de laboratório, há a necessidade de pesquisas que disponibilizem expressões que permitam estimar o MR a partir de resultados de ensaios mais simples que o triaxial cíclico e usuais na pavimentação. Nesta pesquisa, foram realizados ensaios triaxiais cíclicos para a determinação do MR de três solos empregados em rodovias de Campo Grande - MS. A partir dos resultados dos ensaios triaxiais cíclicos, verificou-se o desempenho dos modelos mais comumente empregados para se representar a variação do módulo de resiliência em função do estado de tensão. Foram propostas e analisadas expressões matemáticas entre o MR obtido a partir dos ensaios triaxiais cíclicos e o módulo tangente inicial proveniente de ensaios de compressão simples, sob diversos níveis de tensão. Finalmente, analisou-se a existência de relações que englobem, além dos solos estudados nesta pesquisa, os solos estudados anteriormente em outras pesquisas desenvolvidas na EESC-USP. Os resultados mostram que este tipo de associação é promissora, mas exige-se que o universo de solos estudados seja ampliado para que se estabeleça uma inferência decisiva.The resilient modulus knowledge (MR) is fundamental for pavement design, once it is necessary for stresses, strains and deflections calculus in its layers and subgrade, as well as, the analysis of system performance. Although field tests may be used to determine the dynamic behavior of soils, most of researchers favor laboratory tests, based on the fact that such tests are less constrained because of their carefully controlled conditions. Because laboratory procedures are considered complex and highly expensive, it is desirable to establish relationships among MR and other index properties that are relatively simple and usual in pavement construction. In this research, cyclic triaxial tests were performed to determine MR of three soils used in Campo Grande-MS roads. The performance of the models most commonly adopted to represent resilient modulus as a function of state of stress were verified. A mathematical expression among MR, obtained from the cyclic triaxial tests, and the initial tangent modulus, obtained from unconfined compression strength tests, were developed considering different states of stress. Finally, were analyzed the existence of relationships among soils studied in this research, and soils used in previous studies developed at EESC-USP. Results show that this type of empirical correlation presents a satisfactory results, however incisive conclusions cannot be taken without a large number and variety of soils.
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Silva, Rubens Elias da. "Guiados por mares e peixes: Memória social, inovação tecnológica e o processo de fragmentação na pequena pesca comercial simples em duas comunidades pesqueiras no Rio Grande do Norte." Universidade Federal da Paraíba, 2012. http://tede.biblioteca.ufpb.br:8080/handle/tede/7281.
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Previous issue date: 2012-03-26Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This work aims to understand the impact of new technologies incorporated in fishery production in Barra do Cunhaú and Baía Formosa in the northeastern Brazilian state of Rio Grande do Norte, from the standpoint of fishermen and members of their communities regarding the impact of social changes in the current context of modernization. In this study, I attempt to analyze "the way of life" through the qualitative method supported by ethnography, with reference to the social memory of the fishermen and their communities as well as their daily social practices in light of the social changes which have occured within the area of fishery production, and how these engender tensions and conflicts in relation to production and daily practices. These tensions can be attributed to urban restructuring due to the growth of tourism in the region and the incorporation of new technologies in the daily life of these coastal communities. From this standpoint, the transformation of the way of life peculiar to those in a process of modernization, affected the legitimacy of the social construct of honor connected with fishing. What stands out is the fragmentation of the fishing craft as a job, and as a result, the development of the current situation of social vulnerability caused by precarious working conditions which are in opposition to the development of the work technique whose interest is the pursuit of profit - economic rationality, a characteristic of modern urban industrial societies.
Este trabalho objetiva compreender o impacto das novas tecnologias inseridas no âmbito da produção pesqueira em Barra do Cunhaú e Baía Formosa, no Rio Grande do Norte, a partir dos relatos de pescadores e comunitários a respeito das transformações sociais ocorridas mediante tal impacto no atual contexto de modernidade. Neste estudo, busco analisar o modo de vida através do método qualitativo amparado pela etnografia, tendo como referência a memória social dos pescadores e comunitários e as práticas sociais cotidianas no presente face às transformações sociais ocorridas no espaço da produção da pesca, e como estas engendram tensões e conflitos, tanto nas relações de produção quanto nas práticas cotidianas. Essas tensões podem ser atribuídas à reestruturação urbana decorrente do crescimento turístico na região e na inserção das novas tecnologias no cotidiano dessas comunidades costeiras. A partir disso, a transformação do modo de vida peculiar àquelas num processo de estilização do cotidiano, afetou a legitimidade do construto social da honra ligada à pesca. Acentua-se, como conseqüência dessas transformações, a fragmentação do trabalho artesanal da pesca e, em virtude disso, o desenvolvimento do estágio atual de vulnerabilidade social causado pelas precárias condições de trabalho que se contrapõem a um desenvolvimento da técnica de trabalho cujo interesse é a busca do lucro racionalidade econômica característica das sociedades modernas urbanas industriais.
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Pereira, Valeska Santana de Sena. "Preval?ncia da infec??o por papilomav?rus humano, herpes simplex tipo 1 e 2 e Chlamydia trachomatis em um segmento da popula??o feminina da grande Natal/RN." Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/13067.
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Previous issue date: 2011-04-25Sexually transmitted diseases (STDs) are among the largest public health problems, especially in developing countries. The acquisition of these infections during early sexual activity is common and many infections have a benign course. However, in some pathogens remain in the state of latency can be reactivated and cause productive infection that may progress to severe forms. In addition, some of them are transmitted vertically resulting in congenital infection, causing immediate damage or long-term child. The classic risk factors for sexually transmitted agents are: early onset of sexual and reproductive health, multiple sexual partners throughout life, use of oral contraceptives and co-infections with different pathogens. We present the results of a cross-sectional study aimed to estimate the prevalence of genital infection by human papillomavirus (HPV), Herpes simplex virus (HSV) and Chlamydia trachomatis (CT) in a segment of the female population of the metropolitan area Christmas, among those who enrolled voluntarily sought, Basic Health Units for the examination of cancer screening cervix in the period 2008 to 2010. All participants, a total of 261 women answered a standard questionnaire by which identified the socio-demographic characteristics, classical risk factors for STDs, reproductive and sexual activity and smoking. Of each patient were obtained two samples, one for the completion of the Pap test for detection of cellular changes and the other processed for DNA extraction and analyzed by PCR (polymerase chain reaction) to detect the three pathogens studied. The population of the study was composed of sexually active women aged between 13 and 79 years, mean 38.7 years, most of them being married, low education levels and low incomes. The majority (87%) had normal results on cytology and only 2.7% had low-grade cytological abnormalities. Prevalence rates were 37.9% for HPV, 4.6% for CT and 26% for HSV. HPV prevalence was higher in women under 25, unmarried and in those who had multiple sexual partners. Women with simultaneous infection by HSV-1 and 2 had higher prevalence of HPV infection. The prevalence of HSV infection showed no association whatsoever with the risk factors analyzed and HSV-1 was the predominant type among the cases of genital HSV infection. The overall prevalence of C. Trachomatis was relatively low, thus providing greater value in younger women aged less than or equal to 20 years
As doen?as sexualmente transmiss?veis (DSTs) est?o entre os maiores problemas de sa?de p?blica, especialmente em pa?ses em desenvolvimento. A aquisi??o dessas infec??es durante o in?cio da atividade sexual ? freq?ente, por?m muitas dessas infec??es t?m curso benigno. Entretanto, em algumas o pat?geno permanecer em estado de lat?ncia podendo ser reativado e causar infec??o produtiva que podem evoluir para formas graves. Al?m disso, alguns delas se transmitem verticalmente, resultando em infec??o cong?nita, causando danos imediatos ou em longo prazo ? crian?a. Os fatores de risco cl?ssicos para agentes sexualmente transmiss?veis s?o: in?cio precoce da vida sexual e reprodutiva, m?ltiplos parceiros sexuais ao longo da vida, uso de contraceptivos orais e co-infec??es por diferentes pat?genos. N?s apresentados os resultados de um estudo transversal, que teve como objetivo, estimar a preval?ncia de infec??o genital pelo Papilomav?rus humano (HPV), pelo v?rus Herpes simples (HSV) e por Chlamydia trachomatis (CT) em um segmento da popula??o feminina da regi?o metropolitana de Natal, arroladas entre aquelas que procuraram voluntariamente, Unidades B?sicas de Sa?de para a realiza??o do exame de rastreamento do c?ncer de colo do ?tero no per?odo de 2008 a 2010. Todas as participantes, num total de 261 mulheres, responderam a um question?rio padronizado por meio do qual foram identificadas ?s caracter?sticas s?cio-demogr?ficas, fatores de risco cl?ssicos para DSTs, atividade sexual e reprodutiva e tabagismo. Foram obtidas duas amostras de cada paciente, uma destinada a realiza??o do exame citol?gico de Papanicolaou para a detec??o de altera??es celulares e a outra processada para a extra??o de DNA, e analisadas por PCR (rea??o em cadeia de polimerase) para a detec??o dos tr?s pat?genos estudados. A popula??o alvo do estudo foi composta por mulheres sexualmente ativas, com idade entre 13 e 79 anos, m?dia de 38,7 anos, sendo a maioria delas casadas, com baixo grau de instru??o e baixa renda. A maioria (87%) apresentou resultado normal no exame citol?gico e apenas 2,7% apresentaram altera??es citol?gicas de baixo grau. Foram encontradas taxas de preval?ncia de 37,9% para HPV, 4,6% para CT e 26% para o HSV. A preval?ncia do HPV foi maior nas mulheres com at? 25 anos, nas solteiras e naquelas que tiveram m?ltiplos parceiros sexuais. As mulheres com infec??o simult?nea por HSV-1 e 2 aprestaram maior preval?ncia de infec??o por HPV. A preval?ncia da infec??o pelo HSV n?o apresentou ind?cio de associa??o com os fatores de risco analisados e o HSV-1 foi o tipo predominante entre os casos de infec??o genital pelo HSV. A preval?ncia geral da C. Trachomatis foi relativamente baixa, apresentado maior valor nas mulheres mais jovens, com idade menor ou igual a 20 anos
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Fusco, Pedro Ehrmann Brasiliense. "Invaginações (plicaturas) da grande curvatura gástrica e da parede anterior do estômago para controle de peso: modelos experimentais." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/5/5132/tde-10032010-114604/.
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INTRODUÇÃO: Muitos procedimentos cirúrgicos e endoscópicos bariátricos realizados atualmente diminuem o volume da luz gástrica de forma isolada ou associados a intervenção sobre o intestino. Uma forma de invaginação ou plicatura gástrica associada ao envolvimento protético do estômago foi usada para tratamento cirúrgico da obesidade. O procedimento foi abandonado devido à elevada taxa de complicações e re-intervenções causadas pelo contato da prótese com as vísceras abdominais. A fundoplicatura a Nissen usada para tratamento de refluxo gastroesofágico leva a emagrecimento pequeno, mas significativo. Na fundoplicatura a Nissen não são usados (e, portanto, não há complicações relacionadas a) secção, grampeamento, anastomose, bandas, anéis ou corpos estranhos. Neste trabalho formulamos a hipótese que a invaginação da grande curvatura gástrica levaria a perda de peso em ratos (Série A - primeira série de experimentos). Confirmada esta hipótese, testamos se a invaginação da parede gástrica anterior teria efeito semelhante (Série B - segunda série de experimentos). A invaginação da parede gástrica anterior evitaria a mobilização do grande omento. MÉTODO: Na Série A, trinta ratos foram sorteados em três grupos. Os dez ratos do primeiro grupo, chamado ACTR- ANEST, foram anestesiados e pesados. Aos dez ratos do segundo grupo, chamado A-CTR-LAP, foram adicionadas laparotomia e manipulação visceral à anestesia. Ao terceiro grupo, chamado A-INV-CURV, foi adicionada uma invaginação da grande curvatura gástrica à anestesia e laparotomia. Os animais da Série A foram pesados novamente no sétimo dia após os procedimentos; pesados, sacrificados e necropsiados no vigésimo - primeiro dia após os procedimentos. Na segunda série de experimentos (Série B), vinte ratos foram sorteados em dois grupos. A parede gástrica anterior foi invaginada em dez ratos no primeiro grupo (B-INV-ANT). A grande curvatura gástrica foi invaginada em dez ratos no segundo grupo (B-INV-CURV). Nesta Série B, os ratos foram pesados semanalmente por quatro semanas, sacrificados e necropsiados no vigésimo - oitavo dia após os procedimentos. RESULTADOS: Na Série A, a média de pesos corporais do grupo A-INV-CURV (311,41g) tornou-se menor que a dos grupos A-CTR-LAP (346,18g) e A-CTR-ANEST (362,48), p<0,001 (ANOVA medidas repetidas). A média de pesos das gorduras peri-testiculares foi significativamente diferente somente entre os grupos A-INV-CURV (4364mg) e A-CTR-ANEST (5059mg), p<0,02 (teste de Dunn). Na Série B, a média de pesos corporais do grupo B-INV-CURV (341,90g) tornou-se menor que a do grupo B-INV-ANT (370,56g) no vigésimo - primeiro dia após os procedimentos, p<0,03 (ajuste de Tukey). Os pesos das gorduras peri-testiculares e os volumes gástricos luminais não foram diferentes no vigésimo - oitavo dia após os procedimentos (sacrifício). CONCLUSÃO: A invaginação da grande curvatura gástrica leva a redução de peso em ratos quando comparada a anestesia isolada, a anestesia seguida de laparotomia, e a invaginação da parede gástrica anterior.BACKGROUND: Many bariatric endoscopic or surgical procedures performed today reduce gastric luminal volume, alone or in combination with a distal enteric intervention. A form of prosthetic wrap of the folded (or plicated) stomach was used in the past for treating obesity with a high rate of prosthesis-related reintervention. Nissen gastric fundoplication used in the treatment of gastroesophageal reflux disease induces a small but significant weight loss without gastric stapling, partitioning, or prosthesis-related morbidity. We hypothesized greater gastric curvature invagination would lead to weight loss in rats (first series of experiments named Set A). Once confirmed this hypothesis, we compared anterior gastric wall and greater gastric curvature invaginations for weight loss (second series of experiments - Set B). The anterior invagination would be technically easier as it would avoid mobilization of the greater omentum. METHODS: In Set A, 30 rats were randomly divided into 3 groups. 10 rats in the first group (A-CTRANEST) were anesthetized and weighed. The rats from the second group (ACTR- LAP) were in addition submitted to a laparotomy plus visceral manipulation. In the third group (A-INV-CURV), invagination of the greater curvature of the stomach was added. All animals were weighed on the 7th and 21st days. They were then autopsied on the 21st day. In Set B, 20 rats were randomized in 2 groups. The anterior gastric wall of 10 rats was invaginated in the first group (B-INV-ANT). The greater gastric curvature of 10 rats was invaginated in the second group (B-INV-CURV). All animals were weighed weekly for 4 weeks. They were then autopsied on the 28th day. RESULTS: In Set A, the mean body weight of the A-INV-CURV (311,41g) group became less than the A-CTR-LAP (346,18g) and A-CTR-ANEST (362,48) groups, p<0,001 (repeated measures ANOVA). The mean weight of the peritesticular fat pad from the A-INV-CURV group (4364mg) was also significantly less than from the A-CTR-ANEST group (5059mg), p<0,02 (Dunn test), the other peritesticular fat comparisons were indifferent. In Set B, the mean body weight of the B-INV-CURV group (341,90g) became less than the B-INV-ANT group (370,56g) at 21 days, p<0,03 (Tukeys adjustment). The mean weight of the peritesticular fat pad and the mean gastric volume were not different at 28 days (sacrifice). CONCLUSION: Greater gastric curvature invagination (plication) significantly reduces weight compared to isolated anesthesia, to anesthesia and laparotomy, and to anterior gastric wall invagination.
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FARIAS, Julianna Santos. "DESENVOLVIMENTO DE UM SIMPLES E NOVO SENSOR PARA FLUTAMIDA À BASE DE NANOTUBOS DE CARBONO OXIDADO E ÓXIDO DE GRAFENO: APLICAÇÃO EM AMOSTRAS DE URINA ARTIFICIAL E FORMULAÇÕES FARMACÊUTICAS." Universidade Federal do Maranhão, 2017. http://tedebc.ufma.br:8080/jspui/handle/tede/1291.
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CAPES, FAPEMA,CNPQ
This paper describes the development of a simple and new sensor electrochemical determination of flutamide in voltamétrica formulations pharmaceutical and artificial urine specimens using a carbon electrode vitreous (ECV) modified with oxidized carbon nanotubes and graphene oxide (NCO-OG), which was named ECV/NCO-OG. Electronic microscopy techniques scanning (SEM) and Raman Spectroscopy were used for the characterization of carbon based materials. The electrochemical response of the analyte front of the ECV/NCO-OG was investigated by cyclic voltammetry techniques (VC) and square wave voltammetry (VOQ). The sensor exhibited a high activity eletrocatalítica for the reduction of flutamide in 0.05 V vs. Ag/AgCl. The parameters experimental influence the response of the electrode was investigated and the optimum conditions were found for the electrode modified with NCO-OG, in Britton-Robinson buffer solution-BR on concentration of 0.1 mol L-1 (pH 5). The proposed sensor presented a wide range of linear response of concentration for the flutamide of 0.1 to 1000 µmol L-1 (or µ g L-1 27.6 to 0.27 g L-1) for n = 15 (R2 = 0.997), limit of detection (LOD), limit of quantification (LOQ), and sensitivity of 0.03 µmol L-1, 0.1 µmol L-1, and 0.30 µmol µA -1 L, respectively. The ECV/NCO-OG was successfully applied to the determination of flutamide in pharmaceutical formulations used in the treatment of prostate cancer and artificial urine samples. The results obtained with the proposed sensor were compared with the method described in the literature and showed a level of 95% confidence, demonstrating that there is no statistical difference between the method of reference and the method proposed. The addition and recovery studies show that the proposed method presents a satisfactory accuracy with average value of 101% recovery ( 1)%. for the fortified samples.
Este trabalho descreve o desenvolvimento de um simples e novo sensor eletroquímico para determinação voltamétrica de flutamida em formulações farmacêuticas e amostras de urina artificial empregando um eletrodo de carbono vítreo (ECV) modificado com nanotubos de carbono oxidado e óxido de grafeno (NCO-OG), o qual foi denominado ECV/NCO-OG. As técnicas microscopia eletrônica de varredura (MEV) e a Espectroscopia Raman foram utilizadas para a caracterização dos materiais à base de carbono. A resposta eletroquímica do analito frente ao ECV/NCO-OG foi investigada através das técnicas de voltametria cíclica (VC) e voltametria de onda quadrada (VOQ). O sensor exibiu uma alta atividade eletrocatalítica para a redução da flutamida em 0,05 V vs Ag/AgCl. Os parâmetros experimentais que influenciam a resposta do eletrodo foram investigados e as condições ótimas foram encontradas para o eletrodo modificado com NCO-OG, em solução tampão Britton-Robinson-BR na concentração de 0,1 mol L-1 (pH 5). O sensor proposto apresentou uma ampla faixa de resposta linear de concentração para a flutamida de 0,1 a 1000 µmol L-1 (ou 27,6 µg L-1 a 0,27 g L-1) para n=15 (R2=0,997), com limite de detecção (LOD), limite de quantificação (LOQ), e sensibilidade de 0,03 µmol L-1, 0,1 µmol L-1, e 0,30 µA µmol-1 L, respectivamente. O ECV/NCO-OG foi aplicado com sucesso para a determinação de flutamida em formulações farmacêuticas utilizadas no tratamento de câncer de próstata e amostras de urina artificial. Os resultados obtidos com o sensor proposto foram comparados com o método descrito na literatura e observou-se um nível de confiança de 95%, demonstrando que não há diferença estatística entre o método de referência e o método proposto. Os estudos de adição e recuperação mostram que o método proposto apresenta uma exatidão satisfatória com valor médio de recuperação de 101% ( 1) %. para as amostras fortificadas.
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Scarlato, Michele. "Sicurezza di rete, analisi del traffico e monitoraggio." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3223/.
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Il lavoro è stato suddiviso in tre macro-aree.
Una prima riguardante un'analisi teorica di come funzionano le intrusioni, di quali software vengono utilizzati per compierle, e di come proteggersi (usando i dispositivi che in termine generico si possono riconoscere come i firewall).
Una seconda macro-area che analizza un'intrusione avvenuta dall'esterno verso dei server sensibili di una rete LAN.
Questa analisi viene condotta sui file catturati dalle due interfacce di rete configurate in modalità promiscua su una sonda presente nella LAN.
Le interfacce sono due per potersi interfacciare a due segmenti di LAN aventi due maschere
di sotto-rete differenti. L'attacco viene analizzato mediante vari software.
Si può infatti definire una terza parte del lavoro, la parte dove vengono analizzati i file
catturati dalle due interfacce con i software che prima si occupano di analizzare i dati di
contenuto completo, come Wireshark, poi dei software che si occupano di analizzare i dati di
sessione che sono stati trattati con Argus, e infine i dati di tipo statistico che sono stati trattati
con Ntop.
Il penultimo capitolo, quello prima delle conclusioni, invece tratta l'installazione di Nagios, e
la sua configurazione per il monitoraggio attraverso plugin dello spazio di disco rimanente su
una macchina agent remota, e sui servizi MySql e DNS. Ovviamente Nagios può essere
configurato per monitorare ogni tipo di servizio offerto sulla rete.
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Hwang, Joe, and 黃守偉. "Automatic Graph Drawing for Simple Graphs." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/62852007564092722674.
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Chang, Chia-Yi, and 張嘉益. "Two Efficient Graph Representations for SimpleTwo Efficient Graph Representations for Simple Graphs." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/91938888012934084888.
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碩士國立臺灣科技大學
資訊管理系
93
Representing graphs is a fundamental data-structuring problem. Adjacency matrices and adjacency lists are two well known representations. The operations on an adjacency matrix which contain adjacency test, inserting/deleting an edge can be done in constant time. However, finding all adjacency vertices of a given vertex will take θ(n) time by using an adjacent matrix. On the other hand, to test adjacency on adjacency lists will take O(deg(i)) time, where deg(i) is the degree of vertex i. In this thesis, we propose two efficient representations which not only support adjacency test in constant time, but also support the adjacency test of a given vertex in θ(deg(i)). Our representation will take θ(n2) time to initialize. However, inserting/deleting an edge only takes constant time. The proposed representations will be very efficient for the problems with a lot of inserting/deleting edge operations.
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Papoutsakis, Ioannis. "Tree Spanners of Simple Graphs." Thesis, 2013. http://hdl.handle.net/1807/35920.
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A tree $t$-spanner $T$ of a simple graph $G$ is a spanning tree of $G$,
such that for every pair of vertices of $G$ their distance in $T$ is at
most $t$ times their distance in $G$, where $t$ is called a stretch
factor of $T$ in $G$. It has been shown that there is a linear time
algorithm to find a tree 2-spanner in a graph;
it has also been proved that, for each $t>3$, determining whether a graph
admits a tree $t$-spanner is an NP-complete problem. This thesis studies
tree $t$-spanners from both theoretical and algorithmic perspectives.
In particular, it is proved that a nontree graph admits a unique tree
$t$-spanner for at
most one value of stretch factor $t$. As a corollary, a nontree
bipartite graph cannot admit a unique tree $t$-spanner for any $t$.
But, for each $t$, there are infinitely many nontree graphs that admit
exactly one tree $t$-spanner. Furthermore, for each $t$, let U($t$) be
the set of graphs being the union of two tree $t$-spanners of a graph.
Although graphs in U(2) do not have cycles of length greater than 4,
graphs in U(3) may contain cycles of arbitrary length. It turns out that
any even cycle is an induced subgraph of a graph in U(3), while no graph in
U(3) contains an induced odd cycle other than a triangle; graphs in U(3)
are shown to be perfect. Also, properties of induced even cycles of graphs
in U(3) are presented. For each $t>3$, though, graphs in U($t$) may
contain induced odd cycles of any length.
Moreover, there is an efficient algorithm to recognize graphs that admit a
tree 3-spanner of diameter at most 4, while it is proved that, for
each $t>3$, determining whether a graph admits a tree $t$-spanner of
diameter at most $t+1$ is an NP-complete problem. It is not known if it
is hard to recognize graphs that admit a tree 3-spanner of general diameter;
however integer programming is employed to provide certificates of tree
3-spanner inadmissibility for a family of graphs.