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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.
1

CaracterizaÃÃo ViscoelÃstica Linear de Misturas AsfÃlticas: OperacionalizaÃÃo Computacional e AnÃlise pelo MÃtodo dos Elementos Finitos / Linear Viscoelastic Characterization of Asphalt Mixes: Computational Operationalization and Analysis using the Finite Element Method

Henrique Nogueira Silva 03 December 2009 (has links)
Uma mistura asfÃltica apresenta um comportamento mecÃnico complexo que pode ser idealizado por um modelo viscoelastoplÃstico, que considera a existÃncia de deformaÃÃes recuperÃveis (elÃstico e viscoelÃstico) e nÃo recuperÃveis (plÃstico e viscoplÃstico). No entanto, o estado da arte da pesquisa brasileira tem considerado um modelo mais restrito, o modelo viscoelÃstico linear. Este modelo trata o comportamento mecÃnico do material como dependente do carregamento e da correspondente taxa (temporal) de aplicaÃÃo, que representa um avanÃo considerÃvel na modelagem mecÃnico-computacional de misturas asfÃlticas frente ao modelo elÃstico linear (clÃssico) comumente empregado em projetos nacionais de dimensionamento de pavimentos. Ainda assim, o modelo viscoelÃstico apresenta alguns inconvenientes que dificultam seu uso. Um primeiro inconveniente à que para uma representaÃÃo compatÃvel com os dados experimentais, a caracterizaÃÃo constitutiva viscoelÃstica exige a manipulaÃÃo de uma grande quantidade de coeficientes da sÃrie de Prony, dificultando o processo de ajuste de curva e posterior manipulaÃÃo da sÃrie. AlÃm disso, o processo formal de interconversÃo entre as propriedades viscoelÃsticas fundamentais, comumente necessÃrio por questÃes operacionais, trata-se de um mÃtodo nÃo trivial. Para facilitar o emprego da teoria da viscoelasticidade (linear) na caracterizaÃÃo de misturas asfÃlticas, o presente trabalho se propÃs ao desenvolvimento de um programa computacional especÃfico que facilita o uso do modelo viscoelÃstico linear. Este programa realiza o ajuste de curva de sÃries de Prony e a interconversÃo entre propriedades viscoelÃsticas fundamentais no domÃnio do tempo, quais sejam, a FunÃÃo FluÃncia D(t) e o MÃdulo de RelaxaÃÃo E(t). Como principal resultado, foi possÃvel aplicar este programa computacional na caracterizaÃÃo de duas misturas nacionais tÃpicas, Areia Asfalto (AA) e Concreto AsfÃltico (CA), mostrando de forma detalhada os passos necessÃrios para uma representaÃÃo constitutiva viscoelÃstica adequada. Ainda como parte dos resultados obtidos, foi avaliada a eficÃcia da tÃcnica de ajuste de curva por MÃnimos Quadrados NÃo Linear (MQNL) para sÃries de Prony, sob a expectativa de incorporaÃÃo desta tÃcnica em versÃes futuras do programa computacional desenvolvido. Para explicitar o avanÃo da simulaÃÃo mecÃnica de pavimentos que o modelo viscoelÃstico possibilita frente ao modelo elÃstico (clÃssico), ao final do trabalho foram realizadas anÃlises computacionais utilizando o MÃtodo dos Elementos Finitos (MEF) para estimar os parÃmetros mecÃnicos de projeto de pavimentos (tensÃes de deformaÃÃes) considerando o modelo viscoelÃstico das misturas asfÃlticas investigadas, AA e CA. / An asphalt mixture has a complex mechanical behavior can be idealized by a viscoelastoplastic model that considers the existence of recoverable (elastic and viscoelastic) and non-recoverable deformations (plastic and viscoplastic). However, the state of the art of Brazilian research has considered a more restricted model, the linear viscoelastic model. This model treats the mechanical behavior of the material as dependent on the load and the corresponding (temporal) rate, which represents a considerable advance in mechanical-computational modeling of asphalt mixtures compared to the linear elastic (classic) model commonly employed on projects of national pavement design. But the viscoelastic model has some drawbacks that hinder its use. A first drawback is that for a representation compatible with the experimental data, the constitutive viscoelastic characterization requires handling a large number of Prony series coefficients, which makes difficult the curve fitting process and subsequent handling of the series. Futhermore, the formal process of interconversion between the fundamental viscoelastic properties, commonly required for operational reasons, is a non-trivial task. In order to enable the employment of the theory of (linear) viscoelasticity in the characterization of asphalt mixtures, this study proposed the development of a specific computer program that facilitates the use of the linear viscoelastic model. This program carries out curve fitting of Prony series and interconversion of fundamental viscoelastic properties in time domain, namely, Creep Compliance D(t) and Relaxation Modulus E(t). As a main result, it was possible to use this program in characterization of two national typical mixtures, Sand Asphalt (SA) and Asphalt Concrete (AC), showing in details the steps necessary for a proper viscoelastic constitutive representation. Also as part of the results, it was tested the efficacy of the technique of curve fitting by Nonlinear Least Squares (NLS) for the Prony series, under the expectation of incorporating this technique in future versions of this ongoing software. In order to explain the advances that viscoelastic model can enable in mechanical simulation of pavement, instead of using the elastic (classic) model, at the end of this study it was performed computational analysis using the Finite Element Method (FEM) to estimate the mechanical design parameters of pavements (stress and strains), considering the viscoelastic model of the investigated asphalt mixtures, SA and AC.
2

Most mezi GLUT a knihovnou pro tvorbu uživatelských rozhraní / Bridge between GLUT and Graphical User Interface Library

Friesse, Jan January 2008 (has links)
This document describes a major problems with creating 3D applications in a graphic library named OpenGL. There are some basic informations about a GLUT library including main advantages and disadvantages and a description of alternative implementations of a GLUT API. Further content is focused on the most familiar graphic libraries for creating user interfaces which should be used to develop the OpenGL applications and with their advantages and disadvantages too. The next part describes a draft of a new GLUT API implementation based on the selected user interface library. Major part of thesis is about implementation of GtkGLUT library. Reader can find this implementation on CD. Last part describes future development plans.
3

Síťový interface k detektoru klíčových slov / Network Interface for Keyword Spotting System

Skotnica, Martin Unknown Date (has links)
A considerable part of the research in computer science is dedicated to speech recognition as the speech-controlled systems become useful in many applications. One of them is the keyword spotting which makes possible to find words in audio data. Such a detector is developed at BUT Faculty of Information Technology. The goal of this work is to propose a network interface to this keyword detector based on client/server architecture. Client connects to the server and sends audio data. Server runs keyword detector with this received data and sends the result of keyword spotting back to client. Finally client visualizes the result and interact with user.
4

Klasifikace zubů na 3D polygonálním modelu čelisti / Tooth Clasification on Jaw 3D Polygonal Model

Hulík, Rostislav January 2010 (has links)
This document discusses a solution for tooth classification on 3D jaw polygonal model. Sequentially, I describe techniques for representation and browsing of polygonal model saved in computer memory, techniques for dental curve detection and finally, creation of surface representing approximated tooth plane. After it, I analyze possibilities of height map creation from jaw model which helps in tooth classification in the scope of entire dental curve context and, as a last step, final detection of these teeth in two dimensions. In the same time, I discuss 3D polygonal model segmentation for border extraction, which separates teeth from the rest of the model. In the end of proposed algorithm, I join these two runs into one final detection and classification process of separate teeth, so presented application can automatically indentify and classify teeth to corresponding names and positions with a minimum user interaction. In a second half of this document, I describe implemented solution. According to primary goal, I propose these techniques forcefully to multiplatform approach and maximal user comfort.
5

Changing Object Appearance by Adding Fur / Changing Object Appearance by Adding Fur

Pražák, Martin January 2008 (has links)
Cílem této práce je demonstrovat možnost renderování srsti přímo do existujících obrazů bez toho, aby bylo po uživateli požadováno překreslení všech pixelů nebo dodání kompletní 3D geometrie a osvětlení. Srst je přidána na povrch objektů pomocí extrakce jejich přibližného tvaru a světelných informací z obrazu a takto získaný objekt je poté přerenderován. Tento přístup je nový v tom, že vysokoúrovňové úpravy obrazu (jako např. přidání srsti), mohou úspěšně vést k vizuálně korektním výsledkům a to i přes omezení nepřesnou geometrií a světelnými podmínkami. Relativně velká množina technik použitých v této práci zahrnuje obrazy s velkým dynamickým rozsahem, metody extrakce 3D tvaru z obrazu, výsledky výzkumu vnímání tvaru a osvětlení a fotorealistické renderování. Hlavním cílem práce je potvrdit koncept popsaný výše. Hlavním implementačním jazykem bylo C++ s použitím knihoven wxWidgets, OpenGL a libTIFF. Renderování bylo realizováno v software 3Delight kompatibilním se standardem Renderman, za pomoci množiny shaderů implementovaných v nativním jazyce Rendermanu.

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