C3 - Artigos Publicados em Periódicos
URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/486
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77 resultados
Resultados da Pesquisa
- ItemO valor da universidade em função do valor da formação superior(2007) Rodrigues, Celso Luiz Lopes
- ItemAnálise numérica da dinâmica de cabos altamente extensíveis(EDGRAF, 2003) Isoldi, Liércio André; Santos, Maria Angela Vaz dosA mecânica de cabos altamente extensíveis deve ser estudada numericamente. Para isso, implementamos computacionalmente a solução de um sistema de equações capaz de descrever o movimento de cabos extensíveis em ruptura. Foi utilizado um sistema local e um sistema global de referência. Empregamos os parâmetros de Euler para representar a rotação relativa entre estes sistemas de coordenadas, evitando assim a singularidade associada aos ângulos de Euler. Foi necessária ainda a inclusão da rigidez flexional nas equações de governo, devido à possibilidade do esforço axial, em alguma parte do cabo, atingir um valor nulo ou negativo. Utilizamos um esquema implícito de diferenças finitas para obtermos a solução numérica das equações de governo. Este modelo numérico foi usado para analisarmos o comportamento dinâmico de um cabo sintético durante e após sofrer uma ruptura. Observamos que a tração estática inicial do cabo é um fator determinante, e que um tempo de ruptura maior possibilita uma melhor dissipação de energia ao longo do cabo, tornando-o menos destrutivo que um cabo que se rompe rapidamente.
- ItemExperimental study of the characteristics of the flow in the first rows of tube banks(2009) Olinto, Cláudio Rodrigues; Indrusiak, Maria Luiza Sperb; Endres, Luiz Augusto Magalhães; Möller, Sergio ViçosaThis paper presents the experimental study of the flow instabilities in the first rows of tube banks. The study is performed using hot wire anemometry technique in an aerodynamic channel as well as flow visualizations in a water channel. In the wind channel three tube banks with square arrangement and pitch to diameter ratios P/D = 1.26, 1.4 and 1.6 were studied. The Reynolds number range for the velocities measurements, computed with the tube diameter and the flow velocity in the narrow gap between tubes was 7 × 104–8 × 104. Continuous and discrete wavelets were applied to decompose the velocity results, thus allowing the analysis of phenomena in time–frequency domain. Visualizations in a water channel complemented the analysis of the hot wire results. For this purpose, dye was injected in the flow in the water channel with a tube bank with P/D = 1.26. The range of the Reynolds number of the experiments was 3 × 104–4 × 104. The main results show the presence of instabilities, generated after the second row of the tube bank, which propagates to the interior of the bank. In the resulting flow, the three orthogonal components are equally significant. The three-dimensional behavior of the flow is responsible for a mass redistribution inside the bank that leads to velocity values not expected for the studied geometry, according to the known literature. The resulting flow process can be interpreted as a secondary flow which is characteristic of tube banks.
- ItemWavelet time–frequency analysis of accelerating and decelerating flows in a tube bank(Elsevier, 2005) Indrusiak, Maria Luiza Sperb; Goulart, Jhon Nero Vaz; Olinto, Cláudio Rodrigues; Möller, Sergio ViçosaIn the present work, the steady approximation for accelerating and decelerating flows through tube banks is discussed. With this purpose, the experimental study of velocity and pressure fluctuations of transient turbulent cross-flow in a tube bank with square arrangement and a pitch-to-diameter ratio of 1.26 is performed. The Reynolds number at steady-state flow, computed with the tube diameter and the flow velocity in the narrow gap between the tubes, is 8 × 104. Air is the working fluid. The accelerating and decelerating transients are obtained by means of start and stop of the centrifugal blower. Wavelet and wavelet packet multiresolution analysis were applied to decompose the signal in frequency intervals, using Daubechies 20 wavelet and scale functions, thus allowing the analysis of phenomena in a time–frequency domain. The continuous wavelet transform was also applied, using the Morlet function. The signals in the steady state, which presented a bistable behavior, were separated in two modes and analyzed with usual statistic tools. The results were compared with the steady-state assumption, demonstrating the ability of wavelets for analyzing time varying signals. © 2005 Elsevier B.V. All rights reserved.
- ItemGeotechnical properties of the Cassino Beach mud(Elsevier, 2009) Dias, Claudio Renato Rodrigues; Alves, Antonio Marcos de LimaKnowledge of the marine soils properties, together with hydrodynamic and climatic data, plays an important role for a better understanding of the dynamic behavior of sandy and muddy coasts. This paper deals with reporting and basic interpretation of two campaigns of exploration and characterization of the mud of Cassino Beach, southern Brazil, carried out during the years of 2004 and 2005. Samples were obtained by means of cores collected at some locations offshore, and were submitted to various laboratory geotechnical tests, including determination of the physical index, grain size distribution, Atterberg limits, and shear resistance by both triaxial and shear vane tests. Results confirm the existence of a very soft soil deposit offshore Cassino Beach, highly plastic, compressible, and viscous, forming an important database for further studies.
- ItemSistema de predição de alarmes em processos industriais por classificação não-supervisionada(2009) Braunstein, Sérgio Halpern; Lerm, André Arthur Perleberg; Lerm, Rafael Andréas Raffi; Werhli, Adriano Velasque; Botelho, Silvia Silva da Costa; Lippe, Edwaldo OliveiraUm sistema de predição de alarmes com a finalidade de auxiliar a implantação de uma política de manutenção preditiva industrial e de constituir-se em uma ferramenta gerencial de apoio à tomada de decisão é proposto neste trabalho. O sistema adquire leituras de diversos sensores instalados na planta, extrai suas características e avalia a saúde do equipamento. O diagnóstico e prognóstico implica a classificação das condições de operação da planta. Técnicas de árvores de regressão e classificação não-supervisionada são utilizadas neste artigo. Uma amostra das medições de 73 variáveis feitas por sensores instalados em uma usina hidrelétrica foi utilizada para testar e validar a proposta. As medições foram amostradas em um período de 15 meses.
- ItemA visual system for distributed mosaics using an auvs fleet(2009) Botelho, Silvia Silva da Costa; Drews Junior, Paulo Lilles Jorge; Galeriano, Marcelo de Paiva; Gonçalves, Eder Mateus NunesThe use of teams of Autonomous Underwater Vehicles for visual inspection tasks is a promising robotic field. The images captured by different robots can be also to aid in the localization/navigation of the fleet. In a previous work, a distributed localization system was presented based on the use of Augmented States Kalman Filter through the visual maps obtained by the fleet. In this context, this paper details a system for on-line construction of visual maps and its use to aid the localization and navigation of the robots. Different aspects related to the capture, treatment and construction of mosaics by fleets of robots are presented. The developed system can be executed on-line on different robotic platforms. The paper is concluded with a series of tests and analyses aiming at to system validation.
- ItemEstudo de Caso Sobre Programação Orientada a Aspectos Utilizando Protocolo RMI(2008) Borges, Felipe da Silva; Freitas, André Luis Castro deEste trabalho apresenta um estudo de caso sobre Programação Orientada a Aspectos e uma comparação com a Programação Orientada a Objetos. O aplicativo utilizado para o estudo combina invocações remotas de métodos, utilizando o RMI (Remote Method Invocation) um protocolo de distribuição muito utilizado em programas que envolvam métodos ou objetos remotos. São abordadas as características básicas que norteiam a Programação Orientada a Aspectos, suas vantagens e desvantagens em relação à Orientação a Objetos e os resultados obtidos com a realização dos devidos testes pelas duas formas de programação propostas nesse estudo de caso.
- ItemUsing augmented state Kalman filter to localize multi autonomous underwater vehicles(2007) Botelho, Silvia Silva da Costa; Neves, Renato Silva das; Taddei, Lorenzo; Oliveira, Vinícius Menezes deThe present paper describes a system for the construction of visual maps ("mosaics") and motion estimation for a set of AUVs (Autonomous Underwater Vehicles). Robots are equipped with down-looking camera which is used to estimate their motion with respect to the seafloor and built an online mosaic. As the mosaic increases in size, a systematic bias is introduced in its alignment, resulting in an erroneous output. The theoretical concepts associated with the use of an Augmented State Kalman Filter (ASKF) were applied to optimally estimate both visual map and the fleet position.
- ItemICTM: an interval tessellation-based model for reliable topographic segmentation(2004) Aguiar, Marilton Sanchotene de; Dimuro, Graçaliz Pereira; Costa, Antonio Carlos da RochaThis work introduces a tessellation-based model for the declivity analysis of geographic regions. The analysis of the relief declivity, which is embedded in the rules of the model, categorizes each tessellation cell, with respect to the whole considered region, according to the (positive, negative, null) sign of the declivity of the cell. Such information is represented in the states assumed by the cells of the model. The overall configuration of such cells allows the division of the region into subregions of cells belonging to a same category, that is, presenting the same declivity sign. In order to control the errors coming from the discretization of the region into tessellation cells, or resulting from numerical computations, interval techniques are used. The implementation of the model is naturally parallel since the analysis is performed on the basis of local rules. An immediate application is in geophysics, where an adequate subdivision of geographic areas into segments presenting similar topographic characteristics is often convenient.