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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
441

Propostas de codigos ortogonais para sistemas OCDMA / Construction of optical orthogonal codes for use in OCDMA fiber-optics systems

Domingos Neto, Adriano 26 August 2005 (has links)
Orientador: Edson Moschim / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T21:57:49Z (GMT). No. of bitstreams: 1 DomingosNeto_Adriano_D.pdf: 1544823 bytes, checksum: f09f4717b59d1cce526b7c8746e53efb (MD5) Previous issue date: 2005 / Resumo: Nesta tese, propõe se três novas construções de códigos ortogonais ópticos (OOC), do tipo congruentes, tendo como base a estrutura algébrica do grupo multiplicativo do corpo de Galois GF(p), para aplicação em sistemas de comunicação utilizando a técnica de acesso múltiplo por divisão de códigos ópticos (OCDMA). Os códigos ópticos primos e códigos quadráticos são, pela primeira vez na literatura, gerados a partir de códigos de Slepian (códigos esféricos) e, códigos de resíduos quadráticos, respectivamente. Através do algoritmo da d-cadeia fechada, são obtidos os códigos de primos, como caso particular dos códigos de Slepian. Os códigos quadráticos ópticos são representados por números inteiros quadráticos binários na forma de equações de Diofanto com duas variáveis, de modo que, o reticulado Z2 ou reticulado Â2 fornecem as palavra do código quadrático. O desempenho dos códigos é avaliado usando o critério da probabilidade de erro para situações em que o receptor óptico incorpora um limitador óptico e um fotodiodo APD. O desempenho do sistema é obtido considerando os efeitos da interferência de acesso múltiplo, o ruído balístico do fotodiodo e o ruído térmico do receptor. O desempenho dos códigos propostos é comparado ao desempenho de códigos amplamente divulgados em literatura técnica. Mostra-se ainda que os códigos propostos apresentam desempenho semelhante aos códigos divulgados, tendo como vantagem uma estrutura algébrica de simples implementação e melhor sincronismo / Abstract: This thesis presents a study of optical orthogonal codes (OOe) for application in communication systems using the technique of fiber-optics code division multiple access (OCDMA). The Prime Sequence codes and Quadratic codes are, for the first time in literature, characterized as Slepian group codes (spherical codes) and Quadratic Residues codes, respectively. Through the algorithm of the closed d-chain the Prime Sequence codes are obtained, as a particular case of the Slepian codes. The Quadratic codes are represented by binary quadratic integers in the form of Diophantine equations with two variables, so that, Z2 lattice or Â3 lattice supplies the codeword of the quadratic code. Furthermore, this thesis presents three new constructions of optical orthogonal codes (OOC), construed via congruences having as base the algebraic structure of the multiplicative group of the GaloisField GF(p). The performance of the codes is evaluated using the criterion of the error probability, for situations where the optic receiver incorporates a fiber-optic limiter and a APD photodiode. The performance of the system is evaluated considering the effect of the interference of multiple access, the ballistic noise of the photodiode and the thermal noise of the receiver. The performance of the considered codes is compared with the performance of other codes found in the technical literature. It is observed that the codes considered in this thesis, in this thesis, present similar performance to the reported codes, having as advantage an algebraic structure of simple implementation and better synchronism / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica
442

Teorema de Hodge e aplicaÃÃes

Carlos Augusto David Ribeiro 16 July 2008 (has links)
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O presente trabalho aborda um teorema classico de decomposiÃÃo do espaÃo das p-formas suaves sobre uma variedade Riemaniana compacta e orientada, conhecido como teorema da decomposiÃÃo de Hodge, assim como suas consequÃncias. No decorrer do mesmo, foi feita uma passagem por diversas ferramentas interessantes, como espaÃos Sobolev (capÃtulo 2) e EDP elÃptica (capÃtulo 3), assim como uma abordagem suscinta de formas diferenciÃveis. / This dissertation presents a classical theorem of decomposition of the space of smooths p-forms on compact oriented Riemannian manifold , known as the theorem of Hodge decomposition, and its consequences. During the same was made a passage for several interesting tools, such as Sobolev spaces(Chapter 2) and elliptical PDE (Chapter 3), as well as a succinct approach about diferenciable forms (Chapter 1).
443

Úspory českých domácností a jejich srovnání s vybranými zeměmi EU / Czech Household Savings and their Comparison with Chosen Countries of the European Union

Horáková, Marie January 2012 (has links)
This Master's thesis focuses on Czech household savings. It describes the most important traditional and alternative financial products used by Czech households. Next it reveals the reasons why Czech households are so conservative in their attitude to their financial means in comparison with other European countries. In the last part of this thesis the most important determinants of household savings are identified and with the help of correlation coefficient the intensity of correlation between gross household savings and their determinants is explored.
444

Proofs of Ibukiyama’s conjectures on Siegel modular forms of half-integral weight and of degree 2 / 重さ半整数の2次ジーゲル保型形式についての伊吹山予想の証明

Ishimoto, Hiroshi 23 March 2022 (has links)
京都大学 / 新制・課程博士 / 博士(理学) / 甲第23673号 / 理博第4763号 / 新制||理||1683(附属図書館) / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)准教授 市野 篤史, 教授 雪江 明彦, 教授 池田 保 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM
445

Mixed Witt rings of algebras with involution

Garrel, Nicolas 04 April 2024 (has links)
Although there is no natural internal product for hermitian forms over an algebra with involution of the first kind, we describe how tomultiply two ε-hermitian forms to obtain a quadratic form over the base field. This allows to define a commutative graded ring structure by taking together bilinear forms and ε-hermitian forms, which we call the mixedWitt ring of an algebra with involution. We also describe a less powerful version of this construction for unitary involutions, which still defines a ring, but with a grading over Z instead of the Klein group. We first describe a general framework for defining graded rings out of monoidal functors from monoidal categories with strong symmetry properties to categories of modules. We then give a description of such a strongly symmetric category Brₕ(K, ι) which encodes the usual hermitian Morita theory of algebras with involutions over a field K. We can therefore apply the general framework to Brₕ(K, ι) and theWitt group functors to define our mixed Witt rings, and derive their basic properties, including explicit formulas for products of diagonal forms in terms of involution trace forms, explicit computations for the case of quaternion algebras, and reciprocity formulas relative to scalar extensions. We intend to describe in future articles further properties of those rings, such as a λ-ring structure, and relations with theMilnor conjecture and the theory of signatures of hermitian forms.
446

A classificação das formas binárias aplicada em máquinas de catástrofes /

Oliveira, Alessandra Roberta Custodio de. January 2010 (has links)
Orientador: Eliris Cristina Rizziolli / Banca: Aldício José Miranda / Banca: Carina Alves / Resumo: Este trabalho trata da classificação geométrica das formas binárias quádricas e cúbicas. Além disto, aplicamos esta classificação ao estudo de máquinas de catástrofes / Abstract: This work make reference of the geometry classification of the two variables quadratic, cubic and quartic forma. Before that, the aplication that classification in study of the catastrophe machines / Mestre
447

"I can tell a story that my dads friend tell me" : A corpus- and interview-based study on grammar education, with focus on verb forms.

Lorenzi, Mikaela, Bergström, Sofia January 2015 (has links)
This study consists of two methods: textual analysis and interviews, which are based on text from The Uppsala Learner English Corpus (ULEC), and teachers as interview objects. The textual analysis investigates errors made by students in year seven and year nine, regarding the construction of different verb forms in written English essays. A potential difference between errors made in year seven and nine is also examined. Moreover, the interview based analysis investigates professional junior high school teachers’ teaching methods and attitudes towards grammar. The errors investigated in the textual analysis are compared with the responses of the teachers’ perception of common errors in verb forms made by their students.    The textual analysis showed that the most common errors made regard spelling within the verb phrase, auxiliary verbs, subject-verb agreement, and irregular verbs, and that year seven had a higher frequency of errors than year nine in most categories, even if the results differed inconsiderably.    The analysis of the interviews of the teachers found that teachers, in general, enjoy grammar, and aim to have a student-centered approach, however, the teachers testify of characteristics of traditional teacher-centered grammar teaching. It is reasoned that traditional teacher-centered grammar teaching is fundamentally established, where teachers today appear not to acquire the tools to move away from the teacher-centered approach onwards to a student-centered grammar teaching.    We reason that the education of L2 teachers needs to be reformed and provide tools to help teachers achieve a student-centered approach, and therein enable students to become more successful in grammar.
448

Integration of relational database metadata and XML technology to develop an abstract framework to generate automatic and dynamic web entry forms

Elsheh, Mohammed Mosbah January 2009 (has links)
Developing interactive web application systems requires a large amount of effort on designing database, system logic and user interface. These tasks are expensive and error-prone. Web application systems are accessed and used by many different sets of people with different backgrounds and numerous demands. Meeting these demands requires frequent updating for Web application systems which results in a very high cost process. Thus, many attempts have been made to automate, to some degree, the construction of Web user interfaces. Three main directions have been cited for this purpose. The first direction suggested of generating user interfaces from the application's data model. This path was able to generate the static layout of user interfaces with dynamic behaviour specified programmatically. The second tendency suggested deployment of the domain model to generate both, the layout of a user interface and its dynamic behaviour. Web applications built based on this approach are most useful for domain-specific interfaces with a relatively fixed user dialogue. The last direction adopted the notion of deploying database metadata to developing dynamic user interfaces. Although the notion was quite valuable, its deployment did not present a generic solution for generating a variety of types of dynamic Web user interface targeting several platforms and electronic devices. This thesis has inherited the latter direction and presented significant improvements on the current deployment of this tendency. This thesis aims to contribute towards the development of an abstract framework to generate abstract and dynamic Web user interfaces not targeted to any particular domain or platform. To achieve this target, the thesis proposed and evaluates a general notion for implementing a prototype system that uses an internal model (i.e. database metadata) in conjunction with XML technology. Database metadata is richer than any external model and provides the information needed to build dynamic user interfaces. In addition, XML technology became the mainstream of presenting and storing data in an abstract structure. It is widely adopted in Web development society because of its ability to be transformed into many different formats with a little bit of effort. This thesis finds that only Java can provide us with a generalised database metadata based framework. Other programming languages apply some restrictions on accessing and extracting database metadata from numerous database management systems. Consequently, JavaServlets and relational database were used to implement the proposed framework. In addition, Java Data Base Connectivity was used to bridge the two mentioned technologies. The implementation of our proposed approach shows that it is possible and very straightforward to produce different automatic and dynamic Web entry forms that not targeted at any platform. In addition, this approach can be applied to a particular domain without affecting the main notion or framework architecture. The implemented approach demonstrates a number of advantages over the other approaches based on external or internal models.
449

Implications of plasticization on the properties of hot-melt extruded oral dosage forms

Schilling, Sandra Ursula 27 May 2010 (has links)
The influence of plasticization and other formulation factors on the properties of hot-melt extruded dosage forms for the controlled release of water-soluble active compounds was investigated. Citric acid monohydrate was demonstrated to function as a solid-state plasticizer in hot-melt extruded Eudragit® RS PO tablets and in cast films when concentrations below the compatibility limit were employed. Melting of the organic acid and solubilization in the polymer during extrusion were necessary to observe the plasticizing effect. The release rate of diltiazem hydrochloride, used as a high-melting, water-soluble model drug, from melt extruded Eudragit® RS PO matrix tablets increased and became independent of the original drug particle size in the presence of citric acid monohydrate. Thermal analysis of physical mixtures demonstrated that citric acid promoted drug melting during extrusion by interaction and melting point depression. Diltiazem hydrochloride remained amorphous in the final dosage form, and leaching of citric acid monohydrate enhanced drug diffusion by increasing the matrix porosity. Delayed-release matrix pellets with particle sizes below one mm were prepared by hot-melt extrusion, and the influence of the matrix forming polymer and the type and level of plasticizer on the processibility and release properties was investigated. Pellets complied with the USP requirement for delayed release articles to release less than 10% drug at pH 1.2 after 2 hours when plasticized Eudragit® S100 was used as the release-controlling material. High levels of efficient plasticizers had to be employed to decrease the polymeric melt viscosity, increase the process yield and enable extrusion at moderate temperatures to avoid instabilities during processing and storage. The aqueous solubility of the plasticizer further impacted the drug release rate in acid. A novel application of hot-melt extrusion for the preparation of monolithic matrices comprising enteric coated particles was studied. The influence of the mechanical strength of the multiparticulates, pellet loading and nature of the hydrophilic carrier material on the preservation of the delayed-release properties after extrusion was investigated. Soft particles coated with brittle films remained intact when low-melting carriers that did not solubilize the enteric film during extrusion were used, and the dissolution profile was stable over one year. / text
450

Periods of modular forms and central values of L-functions

Hopkins, Kimberly Michele 21 October 2010 (has links)
This thesis is comprised of three problems in number theory. The introduction is Chapter 1. The first problem is to partially generalize the main theorem of Gross, Kohnen and Zagier to higher weight modular forms. In Chapter 2, we present two conjectures which do this and some partial results towards their proofs as well as numerical examples. This work provides a new method to compute coefficients of weight k+1/2 modular forms for k>1 and to compute the square roots of central values of L-functions of weight 2k>2 modular forms. Chapter 3 presents four different interpretations of the main construction in Chapter 2. In particular we prove our conjectures are consistent with those of Beilinson and Bloch. The second problem in this thesis is to find an arithmetic formula for the central value of a certain Hecke L-series in the spirit of Waldspurger's results. This is done in Chapter 4 by using a correspondence between special points in Siegel space and maximal orders in quaternion algebras. The third problem is to find a lower bound for the cardinality of the principal genus group of binary quadratic forms of a fixed discriminant. Chapter 5 is joint work with Jeffrey Stopple and gives two such bounds. / text

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