• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 41
  • 38
  • 20
  • 17
  • 8
  • 5
  • 3
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 155
  • 34
  • 14
  • 14
  • 13
  • 11
  • 11
  • 10
  • 9
  • 8
  • 8
  • 8
  • 8
  • 8
  • 7
  • 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.
101

Numerical experiments with FEMLAB® to support mathematical research

Hansson, Mattias January 2005 (has links)
<p>Using the finite element software FEMLAB® solutions are computed to Dirichlet problems for the Infinity-Laplace equation ∆∞(<i>u</i>) ≡ <i>u</i><sup>2</sup><sub>x</sub><i>u</i><sub>xx </sub>+ 2<i>u</i><sub>x</sub><i>u</i><sub>y</sub><i>u</i><sub>xy </sub>+<sub> </sub><i>u</i><sup>2</sup><sub>y</sub><i>u</i><sub>yy </sub>= 0. For numerical reasons ∆<i>q</i>(<i>u</i>) = div (|▼<i>u</i>|<i>q</i>▼<i>u</i>)<i> = </i>0, which (formally) approaches as ∆∞(<i>u</i>) = 0 as <i>q</i> → ∞, is used in computation. A parametric nonlinear solver is used, which employs a variant of the damped Newton-Gauss method. The analysis of the experiments is done using the known theory of solutions to Dirichlet problems for ∆∞(<i>u</i>) = 0, which includes AMLEs (Absolutely Minimizing Lipschitz Extensions), sets of uniqueness, critical segments and lines of singularity. From the experiments one main conjecture is formulated: For Dirichlet problems, which have a non-constant boundary function, it is possible to predict the structure of the lines of singularity in solutions in the Infinity-Laplace case by examining the corresponding Laplace case.</p>
102

Digital Geometry, Combinatorics, and Discrete Optimization

Samieinia, Shiva January 2010 (has links)
This thesis consists of two parts: digital geometry and discrete optimization. In the first part we study the structure of digital straight line segments. We also study digital curves from a combinatorial point of view. In Paper I we study the straightness in the 8-connected plane and in the Khalimsky plane by considering vertical distances and unions of two segments. We show that we can investigate the straightness of Khalimsky arcs by using our knowledge from the 8-connected plane. In Paper II we determine the number of Khalimsky-continuous functions with 2, 3 and 4 points in their codomain. These enumerations yield examples of known sequences as well as new ones. We also study the asymptotic behavior of each of them. In Paper III we study the number of Khalimsky-continuous functions with codomain Z and N. This gives us examples of Schröder and Delannoy numbers. As a byproduct we get some relations between these numbers. In Paper IV we study the number of Khalimsky-continuous functions between two points in a rectangle. Using a generating function we get a recurrence formula yielding this numbers.   In the second part we study an analogue of discrete convexity, namely lateral convexity. In Paper V we define by means of difference operators the class of lateral convexity. The functions have plus infinity in their codomain. For the real-valued functions we need to check the difference operators for a smaller number of points. We study the relation between this class and integral convexity. In Paper VI we study the marginal function of real-valued functions in this class and its generalization. We show that for two points with a certain distance we have a Lipschitz property for the points where the infimum is attained. We show that if a function is in this class, the marginal function is also in the same class. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Manuscript. Paper 6: Manuscript.
103

Numerical experiments with FEMLAB® to support mathematical research

Hansson, Mattias January 2005 (has links)
Using the finite element software FEMLAB® solutions are computed to Dirichlet problems for the Infinity-Laplace equation ∆∞(u) ≡ u2xuxx + 2uxuyuxy + u2yuyy = 0. For numerical reasons ∆q(u) = div (|▼u|q▼u) = 0, which (formally) approaches as ∆∞(u) = 0 as q → ∞, is used in computation. A parametric nonlinear solver is used, which employs a variant of the damped Newton-Gauss method. The analysis of the experiments is done using the known theory of solutions to Dirichlet problems for ∆∞(u) = 0, which includes AMLEs (Absolutely Minimizing Lipschitz Extensions), sets of uniqueness, critical segments and lines of singularity. From the experiments one main conjecture is formulated: For Dirichlet problems, which have a non-constant boundary function, it is possible to predict the structure of the lines of singularity in solutions in the Infinity-Laplace case by examining the corresponding Laplace case.
104

Two View Line-Based Matching, Motion Estimation and Reconstruction for Central Imaging Systems

Mosaddegh, Saleh 17 October 2011 (has links) (PDF)
The primary goal of this thesis is to develop generic motion and structure algorithms for images taken from constructed scenes by various types of central imaging systems including perspective, fish-eye and catadioptric systems. As-suming that the mapping between the image pixels and their 3D rays in space is known, instead of image planes, we work on image spheres (projection of the images on a unit sphere) which enable us to present points over the entire viewsphere suitable for presenting omnidirectional images. In the first part of this thesis, we develop a generic and simple line matching approach for images taken from constructed scenes under a short baseline motion as well as a fast and original geometric constraint for matching lines in planar constructed scenes insensible to the motion of the camera for all types of centralimages including omnidirectional images.Next, we introduce a unique and efficient way of computing overlap between two segments on perspective images which considerably decreases the over all computational time of a segment-based motion estimation and reconstruction algorithm. Finally in last part of this thesis, we develop a simple motion estima-tion and surface reconstruction algorithm for piecewise planar scenes applicable to all kinds of central images which uses only two images and is based on mini-mum line correspondences.To demonstrate the performance of these algorithms we experiment withvarious real images taken by a simple perspective camera, a fish-eye lens, and two different kinds of paracatadioptric sensors, the first one is a folded catadioptric camera and the second one is a classic paracatadioptric system composed of a parabolic mirror in front of a telecentric lens.
105

Prédiction de la localisation des protéines membranaires : méthodes méta-heuristiques pour la détermination du potentiel d'insertion des acides aminés

Laroum, Sami 25 November 2011 (has links) (PDF)
Dans ce travail, nous nous intéressons à la localisation des protéines adressées vers la membrane du réticulum endoplasmique, et plus spécifiquement à la reconnaissance des segments transmembranaires et des peptides signaux. En utilisant les dernières connaissances acquises sur les mécanismes d'insertion d'un segment dans la membrane, nous proposons une méthode de discrimination de ces deux types de séquences basée sur le potentiel d'insertion de chaque acide aminé dans la membrane. Cela amène à rechercher pour chaque acide aminé une courbe donnant son potentiel d'insertion en fonction de sa place dans une fenêtre correspondant à l'épaisseur de la membrane. Notre objectif est de déterminer ≪ in silico ≫ une courbe pour chaque acide aminé, afin d'obtenir les meilleures performances pour notre méthode de classification. L'optimisation, sur des jeux de données construits à partir des banques de données de protéines, des courbes est un problème difficile que nous abordons grâce aux méthodes méta-heuristiques. Nous présentons tout d'abord un premier algorithme de recherche locale permettant d'apprendre un ensemble de courbes. Son évaluation sur les différents jeux de données montre de bons résultats de classification. Cependant, nous constatons une difficulté d'ajustement pour les courbes de certains acides aminés. La restriction de l'espace de recherche grâce à des informations pertinentes sur les acides aminés et l'introduction d'un voisinage multiple nous permettent d'améliorer les performances de notre méthode et en même temps de stabiliser les courbes apprises. Nous présentons également un algorithme génétique développé afin d'explorer de manière plus diversifiée l'espace de recherche de ce problème.
106

Syllabification and Phrasing in Three Dialects of Sudanese Arabic

Abdel-Khalig, Ali 15 July 2014 (has links)
This study is a synchronic derivational analysis of phonological phenomena in three dialects of Sudanese Arabic. Its main goal is to provide a unified prosodic account of syncope and of the phonological processes functioning as strategies of repairing unsyllabified segments in the dialects of Urban Central Sudanese Arabic, Shukriiya, and Hamar. The domains of these processes are argued to follow from the degree of restriction that dialects place on word-level and phrase-level syllabification. To this end, the study proposes an analysis of syllabification in the three dialects that identifies the degree to which word-level syllabification is exhaustive, the segments that may be marked extrasyllabic and the conditions regulating their extrasyllabic status, the phrasal level at which these segments must be syllabified, and the level at which alteration to syllable structure is disallowed. In identifying the degrees of restriction dialects place on syllabification and resyllabification, the analysis provides a principled explanation for the levels of repair of unsyllabified segments as well as the domains of syncope. The study also provides an analysis of word stress and an analysis of phonological phrase formation. By revealing and accounting for the interesting phonological patterns attested in these dialects, the study aims to contribute to the area of Arabic phonology in general and to research on the typology of Arabic dialects in particular. In addition to the analyses proposed, its substantial contribution in this regard is a significant body of original data that is being analysed for the first time. With respect to dialects of Sudanese Arabic, the study represents a new direction of enquiry, one that seeks to disentangle their respective grammars and reveal the interesting ways in which they pattern alike and diverge.
107

Comparative genomic and epigenomic analyses of human and non-human primate evolution

Xu, Ke 12 January 2015 (has links)
Primates are one of the best characterized phylogenies with vast amounts of comparative data available, including genomic sequences, gene expression, and epigenetic modifications. Thus, they provide an ideal system to study sequence evolution, regulatory evolution, epigenetic evolution as well as their interplays. Comparative studies of primate genomes can also shed light on molecular basis of human-specific traits. This dissertation is mainly composed of three chapters studying human and non-human primate evolution. The first study investigated evolutionary rate difference between sex chromosome and autosomes across diverse primate species. The second study developed an unbiased approach without the need of prior information to identify genomic segments under accelerated evolution. The third study investigated interplay between genomic and epigenomic evolution of humans and chimpanzees. Research advance 1: evolutionary rates of the X chromosome are predicted to be different from those of autosomes. A theory based on neutral mutation predicts that the X chromosome evolves slower than autosomes (slow-X evolution) because the numbers of cell division differ between spermatogenesis and oogenesis. A theory based on natural selection predicts an opposite direction (fast-X evolution) because newly arising beneficial mutations on the autosomes are usually recessive or partially recessive and not exposed to natural selection. A strong slow-X evolution is also predicted to counteract the effect of fast-X evolution. In our research, we simultaneously studied slow-X evolution, fast-X evolution as well as their interaction in a phylogeny of diverse primates. We showed that slow-X evolution exists in all the examined species, although their degrees differ, possibly due to their different life history traits such as generation times. We showed that fast-X evolution is lineage-specific and provided evidences that fast-X evolution is more evident in species with relatively weak slow-X evolution. We discussed potential contribution of various degrees of slow-X evolution on the conflicting population genetic inferences about human demography. Research advance 2: human-specific traits have long been considered to reside in the genome. There has been a surge of interest to identify genomic regions with accelerated evolution rate in the human genome. However, these studies either rely on a priori knowledge or sliding windows of arbitrary sizes. My research provided an unbiased approach based on previously developed “maximal segment” algorithm to identify genomic segments with accelerated lineage-specific substitution rate. Under this framework, we identified a large number of human genomic segments with clustered human-specific substitutions (named “maximal segments” after the algorithm). Our identified human maximal segments cover a significant amount of previously identified human accelerated regions and overlap with genes enriched in developmental processes. We demonstrated that the underlying evolutionary forces driving the maximal segments included regionally increased mutation rate, biased gene conversion and positive selection. Research advance 3: DNA methylation is one of the most common epigenetic modifications and plays a significant role in gene regulation. How DNA methylation status varies on the evolutionary timescale is not well understood. In this study, we investigated the role of genetic changes in shaping DNA methylation divergence between humans and chimpanzees in their sperm and brain, separately. We find that for orthologous promoter regions, CpG dinucleotide content difference is negatively correlated with DNA methylation level difference in the sperm but not in the brain, which may be explained by the fact that CpG depleting mutations better reflect germline DNA methylation levels. For the aligned sites of orthologous promoter regions, sequence divergence is positively correlated with methylation divergence for both tissues. We showed that the evolution of DNA methylation can be affected by various genetic factors including transposable element insertions, CpG depleting mutations and CpG generating mutations.
108

Analýza realitního trhu v oblasti okolí Lipenské přehrady

DVORSKÝ, David January 2016 (has links)
Thesis process of basic terms related to the real estate market and real estate sales. The study also addressed overview of our segments in the real estate market in Lipensko, their characteristics, construction, engineering, urban planning, and economic factors. It´s about the village of Horní Planá, Černá v Pošumaví, Frymburk and Lipno nad Vltavou. In Lipno nad Vltavou are always chosen for each segment three representatives who are investigated and subsequently compared. The work also points to the trends in the real estate market in this area.
109

Pontes em estruturas segmentadas pré-moldadas protendidas: análise e contribuições ao gerenciamento do processo construtivo / Bridges in precast prestressed segmented structures: analysis and contributions to the management of the construction process

Anna Rosenblum 14 August 2009 (has links)
Este trabalho tem por objetivo contribuir para a melhoria do gerenciamento do processo construtivo de execução de pontes e viadutos em estruturas segmentadas pré-moldadas protendidas, construídas em balanços sucessivos, com base em uma análise das metodologias adotadas e verificando a viabilidade de implantação de um modelo nos processos de gestão que utilizam métodos industriais para execução de obras de arte especiais. A partir da revisão da literatura técnica disponível e tomando como referência os métodos construtivos utilizados em dois canteiros de obras distintos, analisa-se a metodologia de gerenciamento construtivo adotada visando ao aperfeiçoamento do processo de fabricação e montagem, e consequente redução dos custos, desperdícios e prazos. Dentre os vários aspectos observados, ressalta-se a importância de se utilizar uma ferramenta de gerenciamento de projeto nas obras de pontes pré-moldadas, por se mostrarem um processo industrializado, repetitivo e com funcionamento similar a uma unidade fabril. Neste contexto, esta pesquisa visa fornecer subsídios para que se possam estabelecer diretrizes para uma melhor integração do projeto com a construção e conseqüente melhoria da execução nos canteiros de obras. / This work aims to contribute to the improvement of the construction process of bridges and viaducts in precast prestressed segmented structures built in balanced cantilevers, based on an analysis of the methodologies adopted and assessing the viability of the establishment of a model for management processes that use industrial methods for the execution of special bridges. Following a review of the available technical literature, and taking as reference the constructive methods used in two different construction sites, the constructive methodology is assessed, aiming the improvement of the manufacturing, launching and erection process, and the resulting reduction in costs, waste and time. Among the several aspects examined, we emphasize the importance of the use of a project management tool in precast bridges job sites, as they show themselves to be an industrialized, repetitive process, working almost like a manufacturing unit. This research, thus, proposes to supply subsidies for the establishment of guidelines for a better integration of project and job site, and the consequent improvement of execution in construction sites.
110

The impact of IFRS on the analysts' information environment : the role of accounting policies and corporate disclosure

Mylonas, Georgios January 2016 (has links)
The thesis presents the results of a study on the impact of International Financial Reporting Standards on the analysts information environment. The analysis is concentrated on the role of specific IFRSs and corporate disclosure. The effect of IFRS adoption on the information asymmetry between firms and outsiders is examined through properties of analysts earnings forecasts. A contribution to the existing academic literature is made by examining the role of goodwill, intangible assets and acquisitions before and after IFRS adoption in Europe. The results show that the IFRSs for goodwill, acquisitions and intangible assets are related to improvements in the analysts information environment. Another contribution to knowledge is made by investigating the effect of corporate disclosure quantity on the analysts information environment before and after IFRS adoption. For this purpose, a new approach and text analysis technique to assess the impact of corporate disclosure quantity is developed. This involves the creation of a new custom dictionary and the collection of an extensive set of qualitative data. The results show that corporate disclosure quantity under IFRS, is related to improvements in the analysts information environment but that there are differences in this effect across European countries. The results also demonstrate that the improvements in the accuracy of analysts earnings forecasts are related particularly to disclosure concerning financial instruments and operating segments. Overall, the findings of the thesis suggest that the adoption of IFRS resulted in an increase in the quality of reported earnings, which is likely to derive from higher comparability of financial statements, enhanced transparency and an improved analysts information environment. It is also established that fundamental differences across countries remain after IFRS adoption and that the development and harmonisation of financial reporting standards alone are not sufficient to increase the quality of financial information and decrease information asymmetry between market participants.

Page generated in 0.0416 seconds