Thesis (Ph.D.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references (leaves 106-108)

Made available in DSpace on 2014-06-12T15:59:07Z (GMT). No. of bitstreams: 2 arquivo4842_1.pdf: 796872 bytes, checksum: f32f019baff437f9e947861f8bfdf618 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2003 / O aumento do número de documentos disponíveis na World Wide Web (WWW) traz uma série de novos desafios para a área de Recuperação de Informação (RI). As páginas Web divergem em conteúdo e qualidade além de possuírem uma alta dinâmica. Em adição a estes desafios os engenho de busca estão constantemente lidando com usuários inexperientes e com páginas Web construídas com o intuito de manipular as funções de ranking dos engenhos de busca. Estudos recentes têm mostrado que a performance dos engenhos de busca está longe da ideal. Apesar das evoluções tecnológicas, conseguidas até o momento, permitirem a coleta e o armazenamento de um número cada vez maior de páginas nas bases de índices dos engenhos de busca, a maioria destes sistemas enfrenta vários problemas no momento de classificar as páginas de acordo com a necessidade do usuário, em outras palavras, retornar para o usuário a informação que ele necessita. A maioria dos engenhos de busca analisa as páginas Web como um documento texto simples, não levando em consideração a estrutura na qual a página Web está inserida. Diferentemente das coleções de documentos flat , a WWW corresponde a uma coleção de documentos hipertexto que possuem informações auxiliares que vão além do conteúdo textual, tais como a estrutura dos hiperlinks e o texto dos hiperlinks. Estas informações são chamadas de informações hiper , que em conjunto com as informações texto compõem o conjunto de informações que caracteriza uma página Web. A inadequação de estratégias singulares no processo de recuperação de informações no ambiente Web constitui-se em um forte argumento para mostrar que as técnicas recuperação de informação tradicionais não são suficientes no momento de encontrar informações relevantes na Web. Este trabalho propõe a utilização da estrutura de links da Web com o objetivo de produzir um peso de importância global para cada página Web indexada por um engenho de busca. Este peso, chamado peso de autoridade , é integrado aos engenhos de busca, mais especificamente a função de ranking dos engenhos de busca que passa a utilizar estes pesos juntamente com pesos de similaridade textual, com o objetivo de melhorar a eficácia de recuperação do sistemaPara calcular o peso de autoridade para cada página Web foi elaborado um algoritmo de análise de links, o Global Hybrid Hyperlinked Inducted Topic Search (GHHITS) que foi concebido a partir do estudo dos algoritmos de análise de links préexistentes. Para validar o algoritmo em questão foi implementado o SAAL - Sistema para Armazenamento e Análise de Links - que propõe uma maneira eficiente de armazenar a estrutura de links da Web, e executar o algoritmo proposto sobre esta estrutura. Por fim, são apresentados os resultados obtidos durante os testes que avaliaram a eficácia de recuperação de estratégias de busca que utilizaram o peso de autoridade como componente da função de ranking. Neste trabalho é mostrado, portanto, como as informações estruturais podem ser utilizadas de forma a melhorar a qualidade da resposta retornada por um engenho de busca

In the three main sections of this thesis (chapters II, III, and IV; chapter I consists of definitions) we explore three methods of studying Alexander polynomials of links which are alternatives to Fox' free differential calculus. In chapter II we work directly with a presentation of the link group and show how to obtain a presentation for the Alexander invariant. From this we deduce that the order ideal of the Alexander invariant is principal for links of two or three components (the case of one component is well known) but nonprincipal in general for links of four or more components. In any event we show that only one determinant is needed to obtain the Alexander polynomial. In chapter III we use surgery techniques to characterize Alexander invariants of links of two components in terms of their presentation matrices. We then use this to show that the Torres conditions characterize link polynomials when the linking number of the two components is zero or both components are unknotted and the linking number is two. Chapter IV uses Seifert surfaces to prove a generalization of a theorem of Kidwell which relates the individual degrees of the Alexander polynomial to the linking complexity, to present an algorithm for calculating the Alexander polynomial of a two-bridge link from a two-bridge diagram and to prove a conjecture of Kidwell in the special case of two-bridge links. These results are then used to generate link polynomials from allowable pairs (a concept introduced in chapter III) and these results in turn are used to produce methods of generating allowable pairs. / Science, Faculty of / Mathematics, Department of / Graduate

We study Seifert surfaces for links, and in particular the Kakimizu complex MS(L) of a link L, which is a simplicial complex that records the structure of the set of taut Seifert surfaces for L. First we study a connection between the reduced Alexander polynomial of a link and the uniqueness of taut Seifert surfaces. Specifically, we reprove and extend a particular case of a result of Juhasz, using very different methods, showing that if a non-split homogeneous link has a reduced Alexander polynomial whose constant term has modulus at most 3 then the link has a unique incompressible Seifert surface. More generally we see that this constant term controls the structure of any non-split homogeneous link. Next we give a complete proof of results stated by Hirasawa and Sakuma, describing explicitly the Kakimizu complex of any non-split, prime, special alternating link. We then calculate the form of the Kakimizu complex of a connected sum of two non-fibred links in terms of the Kakimizu complex of each of the two links. This has previously been done by Kakimizu when one of the two links is fibred. Finally, we address the question of when the Kakimizu complex is locally infinite. We show that if all the taut Seifert surfaces are connected then MS(L) can only be locally infinite when L is a satellite of a torus knot, a cable knot or a connected sum. Additionally we give examples of knots that exhibit this behaviour. We finish by showing that this picture is not complete when disconnected taut Seifert surfaces exist.

[pt] Na área de dados interligados, usuários frequentemente utilizam ferramentas de descoberta de links para materializar links sameAs entre diferentes base de dados. No entanto, pode ser difícil especificar as regras de ligação nas ferramentas, se as bases de dados tiverem modelos complexos. Uma possível solução para esse problema seria estimular os administradores das base de dados a publicarem visões simples, que funcionem como catálogos de recursos. Uma vez que os links estão materializados, um segundo problema que surge é como manter esses links atualizados quando as bases de dados são atualizadas. Para ajudar a resolver o segundo problema, este trabalho apresenta um framework para a manutenção de visões e links materializados, utilizando uma estratégia incremental. A ideia principal da estratégia é recomputar apenas os links dos recursos que foram atualizadas e que fazem parte da visão. Esse trabalho também apresenta um experimento para comparar a performance da estratégia incremental com a recomputação total das visões e dos links materializados. / [en] In the Linked Data field, data publishers frequently materialize sameAs links between two different datasets using link discovery tools. However, it may be difficult to specify linking conditions, if the datasets have complex models. A possible solution lies in stimulating dataset administrators to publish simple predefined views to work as resource catalogues. A second problem is related to maintaining materialized sameAs linksets, when the source datasets are updated. To help solve this second problem, this work presents a framework for maintaining views and linksets using an incremental strategy. The key idea is to re-compute only the set of updated resources that are part of the view. This work also describes an experiment to compare the performance of the incremental strategy with the full re-computation of views and linksets.

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This report presents results of an empirical study which investigated how two grade 9 Arts and Culture teachers incorporated mathematics in their Arts and Culture lessons in their classrooms in South Africa. The study was implemented through concept mapping activities undertaken by these Arts and Culture teachers. Data was collected from these concept mapping activities and follow-up interviews with teachers. The analysis of the collected data revealed that teachers grapple with the notion of integration, particularly, when it comes to the transfer knowledge and skills across different learning contexts. Lack of proper training, insufficient teacher knowledge and inadequate support from curriculum designers seem to be the most inhibiting factors for teachers to navigate successfully through the notion of integrated teaching and learning. However, in a bid to deal with these new pedagogical challenges, it was observed that teachers resort to other forms of integration, such as relying on students in order to forge links between subjects of learning. The analysis of data from this study raised important pedagogical issues about the link between integrated teaching and teacher content knowledge, and the apparent need for teachers to transform their identities. Drawing from the theory of situated learning, this study has argued that, although integration between fields of learning is desirable in teaching and learning, it is highly problematic in actual practice. For instance, through this study, it was observed that Arts and Culture teachers struggle to use their knowledge of Arts and Culture and mathematics in order to forge connections between the two fields of learning. The study has also drawn from Bernstein‟s theoretical constructs in order to argue that teachers, particularly those in different learning fields like Arts and Culture and mathematics, intuitively posses different „pedagogical codes‟ which account for their inability to negotiate meaning across different learning contexts. Finally, the study has explored and exploited the argument presented through the van Hiele‟s theoretical framework that students turn to progress quicker in geometry (mathematics) when learning takes place in different styles. I have subsequently used this theoretical framework to argue that connections between Arts and Culture and mathematics should be encouraged at school level, as Arts and Culture could provide an exciting pedagogical environment for the teaching and learning of mathematics, which is often construed to be abstract.

Every two-bridge knot or link is characterized by a rational number p/q, and has a fundamental group which has a simple presentation with only two generators and one relator. The relator has a form that gives rise to a formula for the Alexander polynomial of the knot or link in terms of p and q [15]. Every two-bridge knot or link also has a corresponding “up down” graph in terms of p and q. This graph is analyzed combinatorially to prove several properties of the Alexander polynomial. The number of two-bridge knots and links of a given crossing number are also counted.

Mikhail Khovanov developed a bi-graded homology theory for links in the 3-sphere. Khovanov's theory came from a Topological quantum field theory (TQFT) and as such has a geometric interpretation, explored by Dror Bar-Natan. Marta Asaeda, Jozef Przytycki and Adam Sikora extended Khovanov's theory to I-bundles using decorated diagrams. Their theory did not suggest an obvious geometric version since it was not associated to a TQFT. We develop a geometric version of Asaeda, Przytycki and Sikora's theory for links in thickened surfaces. This version leads to two other distinct theories that we also explore.

A Tactical Data Link (TDL) system has been deployed in many military missions as a winning strategy. The performance of a TDL system is governed by the MAC protocol. The MAC protocol that is able to provide more flexibility and high quality of services is more desirable. However, most MAC protocols implemented in current TDL systems are based on a preprogramming TDMA protocol, in which a time slot schedule is fixed. This thesis presents the new self-organized TDMA protocol based on the existing self-organized slot assignment algorithms and the practical military scenarios as the alternative solution to the current preprogramming TDMA protocol. The self-organized TDMA protocol presented in this thesis is based on the Node Activation Polling Access (NAPA), Virtual Slot (VSLOT), and message based slot assignment algorithms. To evaluate the performance of the designed self-organized TDMA protocol over the preprogramming TDMA protocol, the simulation models for both protocols were implemented and simulated with NS-2 under the specific study scenarios. The results show that the self-organized TDMA protocol offers more flexibility and higher performance than the preprogramming TDMA protocol. In addition, the aspects of stability and security for the self-organized TDMA protocol were discussed. The overall conclusion is that the self-organized TDMA protocol could be a viable alternative for a future TDL system.